Irregular coiling is found in the first volutions in the microspheric forms of most genera, indicating a close relationship with the Miliolidae. Alveolinella is an exception as the proloculus in the microspheric form is perforate and the first volutions are peneroplid in character, suggesting it, Alveolinella, may have a different origin than the other alveolinids.
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There are microscopically lines of growth barely perceptible. The horny operculum has seven volutions. Friele H., 1877: Preliminary report on the Mollusca from the Norwegian North Atlantic Expedition in 1876; Nyt Magazin for Naturvidenskaberne 23: 1–10, 1 pl.
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Ventral saddles are rounded. Gyronaedyceras has a compressed gyroconic shell of about two volutions with an assymmnetrical, subtraingular whorl section having a broadly rounded to subangular venter and flat dorsum. Sutures are essentially straight and transverse. Actinosphonate structures are discretely developed.
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The milk-white, shining shell is small and measures 3.1 mm. It is heavy, elongate-ovate. Its whorls increase regularly in size. The whorls of the protoconch are small, almost completely obliquely immersed in the first of the succeeding volutions.
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The shell is fusiform and turriculate. It has an elevated and acute spire. The twelve whorls are convex and longitudinally costated (twelve ribs on the body whorl). They are transversally sharply striated with 6-7 elevated lines, which run along the volutions.
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The ovoid shell is heavy and yellowish white. It measures 5.3 mm. The small whorls of the protoconch are almost completely immersed in the first of the succeeding volutions. The five whorls of the teleoconch are inflated and increase rapidly in size.
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Maccoyoceras is a genus of nautilids included in the family Trigonoceratidae from the Mississippian of North America (Michigan) and Europe. The shell of Maccoyocerasis evolute, volutions only slightly impressed, whorl section hexagonal. Venter flattened, flanks converging, umbilical shoulder prominent. Siphuncle slender, ventral of whorl center.
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On the smaller volutions of the spire a puckering at and following the suture suggests a second indistinct series of nodules. The aperture is less than half the length of the shell. The siphonal canal is short. The terminal portion of columella is whitish and slightly twisted.
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The size of an adult shell varies between 29 mm and 71 mm. The spire is depressed, with sulcate and finely striate volutions. The shoulder angles are sharp. The color of the shell is yellowish brown or chestnut, with close revolving lines of numerous small chestnut spots.
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The summits of succeeding whorls on the later volutions drop a little anterior to the periphery and permit a narrow plain band to appear above the suture. The periphery of the body whorl is slightly angulated. The base of the shell is short, and well rounded. The aperture is moderately large, and subquadrate.
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The uppermost of the keels on the body whorl revolves up to the spire and forms the angle on the upper volutions. The lowermost carina borders the umbilicus and the next one occupies the middle of the under surface. The longitudinal lamellae are continuous on and between the keels. The aperture is round.
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The bluish-white shell is moderately large, measuring 3.1 mm. Its shape is very elongate-ovate, with a very regular, conic spire. The nuclear whorls are small, obliquely immersed in the first of the succeeding turns, above which a portion of the last two volutions only project. The six post-nuclear whorls are flattened.
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The height of the shell varies between 8 mm and 15 mm. The thin shell thin has a short conical shape. It is rather shining, and somewhat iridescent, owing to the thinness of the calcareous layer above the pearl. It is very pale olive on the body whorl, becoming darker on the upper volutions and reddish at the apex.
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The conic shell is milk-white. Its length measures 4.2 mm. The whorls of the protoconch are smooth, deeply obliquely immersed in the first of the succeeding whorls, above which only a portion of the last two volutions project. The six whorls of the teleoconch are moderately rounded, slightly contracted at the sutures, feebly shouldered at the summits.
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Phaedrysmocheilus is a genus of Early Triassic Tainoceratids (Nautiloidea, Cephalopoda) from Siberia. The shell is a rapidly expanding, moderately involute nautilicone; smooth in the adult stage but laterally ribbed in the juvenile stage. Volutions are convex laterally, arched ventrally, embraced dorsally. Whorl sections change during development from being slightly depressed, early, to slightly compressed later, changing from being relatively wide to relatively high.
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The mouth consists of a whorl separated into three and a quarter volutions. The biggest diameter is about . The whorls have a separation of about in the first volution, and it goes to about at the largest whorl displayed. The specimen has a total of about 32 teeth in the first volution, 36 in the second, and 41 in the last.
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The rest are concave above the convex, oblique ribs (ten on the penultimate whorl) with transverse tubercles on the middle caused liy spiral lirae passing over them. The tubercles are more pronounced upon some of the upper volutions than upon the last two or three. In the upper concavity the threads are finer than those below. The body whorl is attenuated in front and finely lirate throughout.
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The early whorls are flattened, the later ones well rounded. All have the summit feebly shouldered. The whorls are ornamented by very regular well rounded axial ribs which become somewhat enfeebled toward the summit. These ribs have a decided protractive slant on the early whorls, while on the middle turns they are vertical, and on the later volutions they have a decidedly retractive slant.
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Hindeoceras is a genus of nautilids from the middle Devonian of North America, included in the tainoceratacean family Rutoceratidae. The shell of Hindioceras is described as large, gyroconic, with about 2 volutions, whorls being barely in contact. The inner margin or dorsum is broadly flattened to slightly concave, sides well rounded, the outer margin or venter arched. The surface is covered with nodes or spines in a regular rhythmic pattern.
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Haplopleuoceras has a small, strongly ribbed, evolute shell of about 2 volutions. Whorl section is subquadrate, slightly compressed, flanks slightly convex, venter rounded. Ribs are undivided, smooth, moderately concave, and slope forward on the ventro-lateral region to form chevrons pointing toward the aperture. The venter on the outer rim is bisected by a rounded keel bordered by distinct but shallow grooves, interrupting the ribbing in the middle of the chevrons.
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This genus includes the thin-shelled light-colored species, previously included in Drillia W.H. Dall (1918) Notes on the nomenclature of the mollusks of the family Turritidae; Proceedings of the United States National Museum v. 54 (1918) The shell is generally short and stout, the spire often very short. The whorls contain nodulous axial ribs, extending over the whole of the volutions. They are generally without spiral sculpture, or, if present, very weak.
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Titanoceras is an extinct genus in the nautiloid order Nautilida from the Pennsylvanian and Lower Permian of North America and Western Australia. Titanoceras grew to be fairly large, with a tightly spiraled shell that reached a diameter of about 8 in (20 cm +) with about three volutions. The inner coils are partially enveloped by the next outer, resulting in a channel or impression along the inner rim, the dorsum. Otherwise all whorls are visible.
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They are coiled to resemble a small sinistral pupa. This pupoid shape makes this species peculiar, as most species in Turbonilla have a helicoid or planorboid protoconch. It is situated obliquely upon the spire of the whorls of the teleoconch and extending considerably beyond the lateral outline of this. The 12 whorls of the teleoconch are situated rather high between the sutures, somewhat overhanging (this is particularly true of the earlier volutions), and slightly shouldered at the summit.
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Lophoceras is a genus of Nautilids belonging to the tainoceratacean family, Koninckioceratidae, found in Lower Carboniferous sediments in Europe, and named by Hyatt, 1893. The shell of Lophoceras is evolute, large, with a slight impressed zone on the inner rim. In early volutions whorl sections are rounded, but later develop an obtusely angular ventral area and venter that disappears toward the front of the mature body chamber. The suture has an angular ventral saddle, broad shallow lateral lobe, and a dorsal lobe.
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Only the tilted edge of two volutions is apparent, which indicates that the axis of whorls of the protconch is at right angles to the axis of the later ones. The 6¾ whorls of the teleoconch are inflated, strongly shouldered at the summit, and decidedly rounded. They are marked by many weak, irregular axial riblets and very strong, broad, angular, incised, spiral channels. These are crossed by many more or less regularly spaced and subequally developed backward slanting axial riblets.
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They are crossed by strong, rounded, almost vertical axial ribs, which render the summit of the whorls crenulate. Eighteen of these ribs occur upon the third, and nineteen upon the penultimate whorl. The intercostal spaces are about one-half as wide as the ribs, crossed by about twelve fine, subequally spaced, incised spiral lines. The summits of succeeding whorls fall a little anterior to the somewhat angulated periphery of the preceding whorl on the earlier volutions, and gives them a somewhat constricted appearance at the deep sutures.
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The upper volutions are encircled by three principal lirae, and a fourth secondary one at the suture. The points of intersection of these spiral ridges and the oblique costse are produced into quite acute nodules or prickles. The base of the shell is almost flat, ornamented with about six concentric lirae, which are more or less granulous, with the interstices exhibiting strong lines of growth and translucent nacre. The color closely approaches the rest of the surface, varied with brown dots both upon and between the granules.
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Parafusulina is a genus of foraminifera included in the fusulinacean family Schwagerinidae that were extant during the Permian. The shell, or test, of Parafusulina is elongate, up to 65 mm in length, fusiform to subcylindrical in shape, tapering slightly to the bluntly rounded poles. The proloculus is large, followed by seven to nine gradually enlarging volutions, coiled around a straight to irregular axis. Septa are numerous, intensely and regularly fluted, folds of adjacent septa touching and forming numerous chamberlets above the floor of the chambers.
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These are concave at top, thin, convex at the sides, obliquely costated and finely transversely lirated. The costae are rather fine, 14 on the penultimate whorl, subnodose a little above the middle, where the concavity of the whorl commences, attenuated at the upper extremity, and becoming obsolete about the middle of the body whorl. The spiral lirae are not conspicuous, rather far apart, and are not found in the excavation at the upper part of the volutions. The aperture is small, occupying rather more than a third of the entire length.
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The whorls are marked by rather strong, well-rounded axial ribs, which are slightly retractively slanting on the early turns and decidedly so on the later volutions. The intercostal spaces about as wide as the ribs marked by 12 deeply incised spiral pits. Of these the fifth is a mere line, while the first four, the sixth, ninth, and tenth are about twice as wide, and the eighth and ninth and eleventh and twelfth form deep broad pits fully three times the width of the last. The suture is moderately constricted.
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They are marked by very slender, poorly developed, decidedly retractive, axial ribs, of which about 30 occur between the sutures upon the last two volutions. In addition to these axial ribs, the whorls are marked by low, feebly rounded, rather broad spiral cords, of which 6 occur between the sutures, on the second, and 7 upon the third and fourth whorl. The spaces separating the spiral cords are narrow, impressed lines. The intersections of the axial ribs and spiral cords form weak tubercles, while the spaces enclosed between them are roundish pits.
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This genus, almost entirely represented by extinct species, is of slender form and elevated, evenly and gradually acuminate spire, conspicuous development of the spiral lyrae and short aperture. It should evidently be considered especially with Trypanotoma and allies, but it is somewhat of an annectant form, as the American species at least have true ribbing on the nepionic whorls which becomes completely lost on the larger volutions of the shell. It is therefore one of those puzzling exceptions which render an arrangement of the genera in a dichotomous table so difficult and unsatisfactory. The embryo in the type, Pleurotoma basteroti Desm.
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They are marked by narrow decidedly elevated, retractive axial ribs, of which 16 occur upon the first and second, 18 upon the third, and 22 upon the penultimate turn. In addition to the ribs, the whorls are marked between the sutures by four spiral keels, which equal the ribs in strength and render them decidedly nodulous at their junction. The spaces enclosed by the ribs and cords are well impressed rectangular pits whose axis coincides with the spiral sculpture. The sutures are subchanneled, showing a portion of the first basal keel in the last two volutions.
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Acanthonautilus is an extinct genus in the nautilid family Solenochildae (Aipocerataceae) from the Upper Mississippian of North America and equivalent (uL Carb) strata in Europe, first described by Foord in 1896. Acanthonautilus, like Solenochilus, has an involute, globular shell of few volutions that enlargens with fair rapidity, with prominent lateral spines extending from the umbilical area at maturity. The siphuncle in Acanthonautilus is narrower than in Solenochilus and not as sinuous. As with Solenochilus, septal necks on the outer, or ventral, side are straight, but those on the inner, or dosal, side rather than being recumbent are simply curved, cytochoanitic.
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The beginning of the conch is marked by the initiation of 5 spiral lirae, the posterior of which is the broadest, and the anterior, which outlines the periphery, the most elevated. The sculpture is modified on the later volutions by the increasing prominence of the peripheral spiral and that directly behind it, the intercalation of secondaries, and the development of undulatory axials 8 to 10 to the whorl. These are indicated chiefly in the crenulation of the peripheral spirals. The periphery of antepenult whorls is situated a little more than one third of the distance across from the anterior to the posterior suture, outlined by a simple elevated spiral cord.
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The type specimen has probably also lost the first whorl of the teleoconch. The eleven remaining whorls are flattened in the middle, rounding moderately toward the summit and the periphery. They are marked by strong, regular, retractive axial ribs, of which occur on the second of the remaining turns, 16 upon the third, 18 upon the fourth to sixth, 20 upon the seventh and eighth, while upon the remaining volutions they become much enfeebled and less regular. These upon the middle whorls are strongest in the middle, sloping gently toward the summit and the periphery, the slope at the summit lending them a shouldered effect.
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While initially differentiated using the metrics of tooth angle and height, Tapanila and Pruitt considered these characteristics to be intraspecifically variable, reassigning H. ferrieri to H. davisii. H. jingmenense was described in 2007 from a nearly complete tooth whorl with four and a third volutions (part and counterpart) found in the Lower Permian Qixia Formation of Hubei Province, China. It was discovered during road construction. The specimen is very similar to H. ferrieri and H. bessonowi, though it differs from the former by having teeth with a wider cutting blade, and a shorter compound root, and differs from the latter by having fewer than 39 teeth per volution.
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