28 



MOLLUSCA 



The Variously-Ribbed Aramon- 



168. A. VARICOSTATUS 



ite, pi. XX. fig. 8. 



Ammoniies varicostatus. Buckland, Geology and Minera- 

 logy considered, II. p. 62, pi. 42, fig. 7. 



Discoidal, with six two-thirds exposed rounded volutions ; 

 the inner ones crossed by numerous, narrow, greatly elevated 

 close set ribs, which are bifurcated on the rounded ambit ; 

 near to tlie termination of the outer volution the ribs become 

 large, broad, distant, and slightly curved, and are destitute 

 of the dorsal bifurcation ; aperture oblong-ovate. Greatest 

 diameter nine inches. 



Found in the Oxford Clay at Havvnes, four miles south of 

 Bedford. 



169. A. KOTUNDUS The Round Ammonite, pi. XX. 



fig. 10. 



Ammoniies rotundus. Sowerby, Min. Conch. III. p. 169, 

 pi. 293, fig. 3. Fleming, Brit. An. p. 243. De la Beche, 

 Geo. Manuel, p. 374. 



Discoidal ; volutions exposed ; sides crossed by numerous 

 thick ribs, which become bifurcate as they pass over the 

 back ; aperture orbicular, interrupted only by a small sinus, 

 from the insertion of the preceding volution. 



This species is nearly allied to Ammonites biplex, pi. V. 

 fig. 10, but distinguished from it, by the ribs being less 

 numerous, thicker, shorter, and not so regularly bifurcate in 

 passing over the ambit ; some are trifurcate ; the sides are 

 less compressed. 



Found in the Kimmeridge Clay, at Purbecks, and occurs 

 in the Inferior Oolite of Normandy. 



170. A. FiMBKiATUS. — The Fringed Ammonite, pi. XX. 

 fig. 12. 



Ammonites fimbriatns. Sowerby, Min. Conch. 11. p. 145, 

 pi. 161. Fleming, Brit. An. p. 242. De la Beche, Geo. 

 Manuel, p. 372. 



Discoidal ; with cylindrical volutions, the inner ones 

 entirely exposed, crossed by numerous lines of growth, 

 which have fimbriated margins ; aperture orbicular, pro- 

 vided with an undulating frill. 



Found at Lyme Regis, Dorsetshire, in the Blue Lias ; 

 and in the Lias of Yorkshire, and middle and south of 

 England. 



Genus V.— GONIATITES.— Fow Bmh. 



GONIATITKS. 



GiLBERTSONi. — Gilbertson's Goniatite, pi. XXI. 



' Shell discoidal, generally very convex or nearly 

 globose, most of the species deeply umbilicate ; the inner 

 volutions much, or wholly concealed ; with internal, 

 strengthening, transverse ridges. 



1. G. LooNEYi. — Looney's Goniatite, pi. XXI. fig. I, 2, 

 and 3. 



Goniatites Looneyi. Phillips, Geology of Yorkshire, II. p. 

 236, pi. 20, fig. 33, and 35. 



Depressed, glabrous, sides covered with sigmoidal striae ; 

 umbilicus very small ; aperture elliptical ; provided with 

 numerous septa ; the dorsal and lateral sinuses double and 

 widely set ; but merely waved in immature shells. 



Discovered in High-Green Wood, near Todmorden, Hud- 

 dersfield, Lancashire. 



2. G. 



fig. 4, 5. 



Goniati/es Gilbertsoni. Piiillips, Geology of Yorkshire, 

 n. p. 2.36, pi. 20, fig. 27, 28, and 31. 



Depressed ; elliptical, glabrous ; sides covered with greatly 

 bent, minute striae ; umbilicus small ; aperture oblong ; septa 

 numerous, with round lobes and sinuses ; the dorsal sinus 

 double and wide, the lateral sinus simple. 



Locality unknown. Named in honour of Mr Gilbertson, 

 of Preston, a zealous and acute naturalist. 



3. G. PAUciLOBUs. — The Few-Lobed Goniatite, pi. XXI. 



fig. 67. 



Goniatites paucilobus. Phillips, Geology of Yorkshire, 

 II. p. 230, pi. 20, fig. 36 to 38. 



Depressed ; sides with waved striae, and shallow undula- 

 tions ; umbilicus minute ; aperture elliptical ; the lobes and 

 sinuses of all the septa are round ; the first lateral one very 

 large. Distinguished from tlie Goniatites implicatus, fig. 58. 

 by the form of its lateral sinus. 



4. G. DiscREPANs Ths Discrepant Goniatite, pi. XXI. 



fig. 8 and 15. 



Goniatites Loonei/i. Phillips, Geology of Yorkshire, II. 

 p. 236, pi. 20, fig. 32 and 34. 



Discoidal, smooth, with a minute umbilicus ; striae doubly 

 undulating; slightly compressed towards the ambit; aper- 

 ture oblong ovate ; septa numerous, with double, wide dor- 

 sal and lateral sinuses. 



This species difters from the Goniatites Looneyi, fig. 1, 2, 

 and 3, in not being depressed, in the more rounded contour 

 of the disk, in the aperture being more ovate, and sharper 

 next the back, and in the indentation from the volution being 

 more acute. 



Locality unknown. 



5. G. Striolatus. — The Grooved Goniatite, pi. XXI. 

 fig. 9, 10. 



Goniatites striolatus. Phillips, Geology of Yorkshire, II. 

 p. 234, pi. 19, fig. 14 to 19. 



Nearly globular, sides somewhat flattened, ambit broad ; 

 with spiral and transverse, very delicate striae ; umbilicus 

 very small ; aperture ovate ; septa having very wide, acute, 

 dorsal sinuses, and the lateral lobes much widened and 

 rounded. 



This species differs much in its infant and adult condi- 

 tions. When very young it is nearly globular, the umbilicus 

 much larger, in proportion to the size of the disk, and more 

 acute at the edge than in the adult ; the constrictions are 

 more parallel, and the striae more straight and simple. As 

 it advances in age, the sides become more compressed, the 

 constrictions a little undulous, as in fig. 9 ; and when the 

 shell is mature the constrictions become obsolete, and the 

 angularity of the umbilicus is entirely lost; and the septa 

 and striae hardly vary ; as seen in the more elliptical and 

 beautiful contour of fig. 10. 



This species may easily be confounded with the G. 

 obtusus, fig. 11 and 12, but may be distinguished by its sides, 

 being less parallel than those of that shell. 



Found in the Shale, at High-Green Wood, near Hudders- 

 field ; and in Shale, at Kulkeagh, near Enniskillen, Ireland. 



6. G. OBTUSUS — The Obtuse Goniatite, pi. XXL fig. 11, 

 12. 



Goniatites obtiisus. Phillips, Geology of Yorkshire, II. p. 

 234, pi. 19, fig. 10 to 13. 



