Nautilus. 



MOLLUSCA. 



37 



Discovered in the Clialk Marl at Ilumsey, by Dr 

 Maritell. 



Tlie 3'oiiiig of N. elegans, pi. 25, fig. 10, bears a conside- 

 rable lilieness to this sliell, but the striae are stronger in the 

 iV. expaiisus, and the aperture is much more expanded. 



41. N. KADiATus. — The Rayed Nautilus, pi. XXV, 

 fig. 15. 



Nautilus radiatus. Sowerby, Min. Concii. IV. p. 78, 

 pi. S.'iG. Fleming, Brit. An. p. 230. 



Gibbose, umbilicate ; inner volutions one-third inserted, 

 the outer one increasing very rapidly ; sides rounded and 

 ornamented with curved, radiating undulations, which meet 

 upon the back at an obtuse angle ; back or ambit rounded, 

 umbilicus of moderate dimensions, and exposing the inner 

 volutions and the edges of the septa ; aperture nearly circu- 

 lar, its length and breadth being about equal, exceeding in 

 dimensions half the diameter of the disk, and deeply indented 

 by the intrusion of the volutions ; greatest diameter six 

 inches and a half. 



Found in the Greensand Formation, near Maltor. 



In its aspect, this shell appears to resemble N. elegans, 

 pi. 25, fig. 10, and also the N. undulattis, pi. 23, fig. 2. The 

 undulations are more numerous than in the latter, there being 

 at least five or six to each septum, and it is more regularly 

 convex ; besides, the deeply indented ambit of the N. 

 undtdatus, when viewed in profile, will at once distinguish it. 



42. N. DISCUS The Quoit Nautilus, pi. IX. fig. 4. 



Nautilus discus. Sowerbj', Min. Conch. I. p. 39, pi. 13. 

 Fleming, Brit. An. p. 230. 



Discoidal, much compressed ; margins flat, consisting of 

 five entirely exposed volutions ; aperture oblong, its greatest 

 width not exceeding half an inch; its exterior margin nar- 

 rower than the inner one, and furnished with a notch, result- 

 ing from a small groove, which encompasses the margin of 

 the ambit ; chambers numerous ; septa about an eighth of an 

 inch apart ; siphuncle situate nearest the inner edge of the 

 septa. 



Discovered in the dark coloured Limestone, near Kendal, 

 Westmoreland. 



This species was, bj' mistake, engraved among the 

 Ammonites. 



Genus VIII.— NUMMULITES,— Z^awarcA. 



Shell lenticular, disciform, or thick in the middle, and 

 attenuated towards the margins ; spire internal, multilo- 

 cular, covered over by several tables ; volutions gene- 

 rally numerous, sometimes to the number of twenty ; 

 outer partitions complicated, produced, extending and 

 uniting on each side of the centre ; cells very numerous, 

 small, alternate, and formed by transverse, imperforate 

 septa, which are convex near the fronts, leaving a fissure 

 between each of them and the preceding volutions ; 

 their sides narrow, variously curved, and extending to 

 the axis. 



1. N. CoMPTOsi. — Compton's Nummulite, pi. XXVI. 

 figs. 1, 2. 



Nautilus Comptoni. Sowerby, Min. Conch. II. p. 45, pi. 121. 

 Fleming, Brit. An. p. 229. 



Lenticular, obtusely carinated; surface smooth, with about 

 ten distinctly marked septa ; aperture acutely triangular, 

 formed of two arcuated lips ; diameter not a line. 



Discovered by Earl Compton, at Eai'l Stoke, near War- 

 minster, Wiltshire, and named in honour of that scientific 

 nobleman. 



2. N. VARIOLARIA. — The Variable Nummulite, pi. XXVI. 

 figs. 3, 4, 5. 



Numnndaria variolarici. Sowerbj', Min. Conch. VI. p. 76, 

 pi. 538, fig. 3. Lenticulites variolaria, Lamarck, Env. de 

 Paris, p. 168. An. San. Vert, VII. p. 619. 



Shell very convex and smootii, with four or five volu- 

 tions ; margin obtuse ; septa about twenty, forming rays near 

 the margin. 



This species is not above a line in diameter, is subject to 

 considerable variety in thickness, according to its dimensions ; 

 the septa are more or less visible on its surface, as it is more 

 or less opaque. 



Discovered at Stubbington, by J. Holloway, Esq. in 

 Pyrites, in the lower part of the London Clay. 



3. N. L^viGATA. — The Smooth Nummulite, pi. XXVI. 

 figs. 5, 6, 7. 



Numniuliles lavigata. Lamarck, Env. de Paris, p. 172. 

 An. San. Vert. VII. p. 629. Parkinson, Org. Rem. III. 

 p. 152 and 158, pi. 10, figs. 13, 14. Mantell, Geo. Sussex, 

 p. 269. Sowerby, Min. Conch. VL p. 75, pi. 538, fig. 1. 

 Nummulita loBvigata, Fleming, Brit. An. p. 233. 



Lenticular, smooth, consisting of about twelve greatly 

 compressed volutions ; sides convex, a little plain, except 

 having a few elevated dots, and in the centre being slightly 

 undulated ; margin narrow, somewhat obtuse, and very finely 

 striated ; aperture narrow. 



This shell is composed of perpendicular fibres, with an 

 external and internal semitransparent coating. 



Discovered at Stubbington Cliff, by J. Holloway, Esq. It 

 has since been found in Bricklesom Bay, Sussex. 



Genus IX.— BELLEROPHON.— ilfowO^or^ 



Shell thick, univalve, unilocular, involute, umbilicate 

 on both sides, nearly symmetrical, bicarinated, and 

 almost spherical, the last volution enveloping the 

 others ; aperture very large, semilunate, arched, and 

 terminated by the extremities of the columella or axis, 

 which is transverse, and provided with a sinus or notch 

 in tlie outer edge of the lip, between the keels. 



SECTION I. SHELLS WITH A MESIAL CARINA. 



1. B. TANGENTiALis. — The TaDgent-RIdged Bellerophon, 

 pi. XXVI. figs. 12 and 22. 



Bclleroplioa tangentialis. Phillips, Geo. of Yorkshire, II. 

 p. 230, pi" 17, figs. 6, 7, and 14. 



Cylindrico-globose ; umbilicus largely rounded ; aperture 

 much expanded ; ambit broad, and provided with an acute, 

 narrow carina, from which emanate straight ridges and fur- 

 rows, which rise perpendicular to the keel, forming tangents 

 to the inner margin. 



Found at Bolland, Queen's County, Ireland. 



