244 MOLLUSCA. CEPHALOPODA. Ammonita. 



45. A. Parkinsoiii Whorls numerous, exposed ; ribs numerous, elevated, 



slightly arched, bifid near the front, which is very narrow, and plain ; aper- 

 ture oblong. — Sower. Miii. Conch, t. cccvii. — In Lias, Bath. 



4C. A. dentata. — AVhorls increasing rapidly, inner ones much concealed, 

 umbilicate, front square ; ribs prominent, and forked near their commence- 

 ment, terminating upon the edges of the front. — A. serratus {Parkinson^ 

 Trans. Geol. v. 57.) Sower. Min. Conch, t. cccviii Clmlk-Marl. 



47. A. perampla Discoid, whorls 4, half concealed, ventricose, front 



rounded, plain ; ribs few, large, obtuse ; aperture transversely ovaL — Man- 

 teirs Fossils of the South Downs, p. 200 — Soiver. Min. Conch, t. ccclvii. — In 

 Chalk., South Downs. 



48. A. Lewesiensis. — Whorls rapidly increasing in size, depressed, the inner 

 ones half exposed ; ribs large and obtuse ; front narrow, rounded, plain ; 

 aperture sagittate. — ManteWs Fossils, p. 199. t. 22. f. 2 — Sotaer. jMin. Conch, 

 t. ccclviii. — In Chalk, Lewes. 



49. A. plicomphala. — Discoid, umbilicate, with eight or ten diverging sharp 

 ridges, extending over a part of the sides ; front rounded, plain ; aperture 

 ovate. In the young state, the front is transversely fuiTowed — Sower. INIin. 

 Conch, ccclix. and cccciv — In Sandstone (Middle Oolite ?) Bolingbroke, Lin- 

 colnshire. 



50. A. Smithii Depressed, ribbed and keeled ; inner whorls few, almost 



wholly exposed ; ribs slightly curved ; keel obtuse ; sides flattened ; aperture 

 oblong. — Sower. Min. Conch, t. ccccvi. — In Chalk Marl. 



5L A. striatula. — Discoid, carinated, radiated ; sides of the whorls convex ; 

 the inner whorls exposed ; radii numerous, slender, undulated ; surface co- 

 vered with minute striae, parallel to the radii ; aperture elliptical Sower. 



Min. Conch, t. ccccxxi. f. 1 — In Marly Limestone, Scarborough. 



52. A. suhradiata. — Lenticular, umbilicated, carinated, and radiated ; radii 

 twice curved, obscure, excepting near the margin, where they are bifid ; 

 umbilicus small ; keel entire ; aperture sagittate. — Sower. Min. Conch, 

 ccccxxi. f. 2. — Oolite, between Bath and Bristol. 



53. A. parva. — Discoid; surface marked with divergmg, undulating, striae; 

 inner whorls exposed ; front rounded : aperture oval — Soiver. ^lin. Conch, 

 t. ccccxlix. f. 2 Tunbridge. 



54. A. IcBviuscula. — Discoid, carinated, umbilicated, obscurely radiated ; ca- 

 rina distinct ; radii waved, alternately long and short, slightly elevated ; um- 

 bilicus small, exposing part ot the inner whorls ; aperture sagittate. — Sotcer. 

 Min. Conch, t. ccccli. f. 1. 2 — In Oolite, Dundry. 



55. A. corrugata — Discoid, carinated and umbilicated, strongly radiated ; 

 carina distinct ; radii waved, sometimes furcated, elevated ; umbilicus broad, 



exposing parts of the inner whorls ; aperture obovate ; front obtuse Sower, 



Min. Conch, t. ccccli. f 3. — In Oolite, Dundry. 



56. A. Turneri. — Depressed, radiated, carinated, a fiiri'ow on each side of 

 the keel ; inner whorls exposed ; radii numerous, equal, curved towards the 

 front; aperture oblong, quadrangular — Sower. Mm. Conch, t. cccclii. — In 

 Lias, Wymondham Abbey and Walchet. 



*** Whorls hnohbed. 



57. A. tiodosa Depressed, keeled, ribs straight for two-tliirds of their 



length, then rising into a small knob, from which they extend towards the 

 keel, curving upwards, rather distant, with a gentle concavity between them; 



