244 
MOLLUSCA. CEPHALOPODA. Ammonita. 
45. A. ParMnsoni — Whorls numerous, exposed ; ribs numerous, elevated, 
slightly arched, bifid near the front, which is very narrow, and plain ; aper- 
ture oblong Sower. Min. Conch, t. cccvii. — In Lias^ Bath. 
46. A. dentata. — Whorls 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. — Chalk-Marl. 
47 . A. perampla Discoid, whorls ^4, half concealed, ventricose, front 
rounded, plain ; ribs few, large, obtuse ; aperture transversely oval. — Man- 
telVs Fossils of the South Downs, p. 200. — Sower. 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. — MantelVs Fossils, p. 199. t. 22. f. 2 — Sower. Min. Conch, 
t. ccclviii. — In Chalk, Lewes. 
49. A. pUcomphala. — 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 furrowed — Sower. Min. 
Conch, ccclix. and cccciv.— -In Sandstone (Middle Oolite ?) Bolingbroke, Lin- 
colnshire. 
50. A. (S'miii'iM.— 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. 
51. A. striatula. — Discoid, carinated, radiated ; sides of the whorls convex ; 
the inner whorls exposed ; radii numerous, slender, undulated ; surface co- 
vered v/ith 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 
tvvdce 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 diverging, undulating, striae ; 
inner whorls exposed ; front rounded : aperture oval —Sower. Min. Conch, 
t. cccexlix. f. 2 — Tunbridge. 
54. A. Iceviuscula. — Discoid, carinated, umbilicated, obscurely radiated ; Ca- 
rina distinct ; radii waved, alternately long and short, slightly elevated ; um- 
bilicus small, exposing part of the inner whorls ; aperture sagittate. — Sower. 
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, eleA^^ated ; umbilicus broad, 
exposing parts of the inner whorls ; aperture obovate ; front obtuse Sower. 
Min. Conch, t. ccccli. f. 3. — In Oolite, Dundry. 
56. A. rMrnm.— Depressed, radiated, carinated, a furrow on each side of 
the keel ; inner whorls exposed ; radii numerous, equal, curved towards the 
front; aperture oblong, quadrangular.— *S'owcr. Min. Conch, t. cccclii.— In 
Lias, Wymondham Abbey and Walchet. 
Whorls knohhed. 
57 . A. nodosa — Depressed, keeled, ribs straight for two-thirds 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 
