246 MOLLUSCA. CEPHALOPODA. Ammonita. 
in a tubercle ; apertures transverse, quadrangular, three times as wide as 
long. — Sower. Min. Conch, t. cci. (indistinct.) — Under Oolite. 
71. A. Discoid, carinated, whorls 4, inner ones half concealed, 
about eight spiniform tubercles upon each whorl ; keel round, entire ; aper- 
ture elliptical. Var. a. aperture circular; keel sometimes impressed. — Sower. 
Min. Conch, t. ccxiii. — Under Oolite. 
72. A. Discoid, inner whorls half exposed, with large tubercles 
on each side ; marginal undulations many, central ones feAv, rising into tu- 
bercles ; front rounded with a distinct keel ; aperture cordate Soiver. Min. 
Conch, t. cclxiii. f. 4, 5. — Under Oolite^ Dundry. 
73. A. BirchL — Discoid, whorls 6, exposed, increasing gradually, sides con- 
cave, front rounded, transversely and obscurely sulcated ; two involuted rows 
of spiniform tubercles ; aperture transverse.- — Sower. Min. Conch, t. cclxvii. 
— In Lias at Lyme. 
74. K.lauta — Discoid, inner whorls half concealed; front narroAv, slightly 
concave; principal ribs slender, varicose or tuberculated near their com- 
mencement, shorter ribs alternating, united in pairs, to form compressed tu- 
bercles upon the edges of the front. — {Park. Trans. Geol. v. 58.) Sower. Min. 
Conch, cccix. — Mant. Suss- 91. t. xxi. f. 11. — Chalk Marl. 
75. A. tuberculata — Whorls gibbose, half concealed ; front rather flat ; ribs 
arising in threes from large round tubercles, and uniting in pairs to form 
large compressed tubercles upon each edge of the front ; aperture suborbicu- 
lar. — Sower. Min. Conch, t. cccx. f. 1, 2, 3. — Chalk Marl. 
76. K. 'proboscidea. — Whorls ventricose, partly concealed ; front concave, tu- 
bercles upon the sides of the last whorl, and both edges of the front subcylin- 
drical; aperture orbicular. — Sower. Min. Conch, t. cccx. f. 5 — Chalk Marl. 
77* K. Gulielmii. — Lenticular, with a narrow front; whorls exposed; ribs 
dissimilar, terminating in small tubercles, principal ribs furnished with tivo 
tubercles near their commencement ; aperture elliptical — Sower. Min. Conch; 
t. ccxi. — Middle Oolite. 
78. A. Davossi — Whorls exposed ; sides nearly flat, with numerous ribs, 
and a few distant obtuse tubercles, each tubercle connected with about 4 sul- 
ci ; aperture nearly orbicular — Sower. Min, Conch, t. cccl. — In Lias.^ Dorset- 
shire. 
79. A. Brodiaei Largely umbilicate, gibbose; ribs radiating, large, nu- 
merous, terminating on the sides of the whorls by obtuse tubercles, front 
rounded, plicated; aperture transverse!}" oblong, curved — Sower. Min. Conch, 
t. cccli.— Oolite, 
80. A. perarmata. — Depressed, whorls exposed; front rounded, armed 
with two concentric rows of large pointed tubercles, connected by obtuse 
ridges; aperture nearly orbicular — Sower. Min. Conch, t. ccclii. — Under 
Oolite. 
81. A. mutabilis. — Depressed ; outer whorls compressed, plain and smooth ; 
inner' whorls two-thirds exposed, tuberculated, plicated; plicm interrupted 
over the front ; aperture ovato-sagittate. — In the young state the front is 
flattened Sower. Min. Conch, ccccv.— -In Chinch Clay ot the Middle Oolite 
near Horn Castle. 
82. A. subarmata Depressed, concave, ribbed, inner whorls almost wholly 
exposed ; ribs curved, often united in pairs by smooth spines ; aperture trans- 
versely oblong, arched; the spines disappear on', the last Avhorl — [Young and 
Bird's Geol. of Yoik. 250. t. 13. f. 3.) Sower. Min. Conch, t. ccccvii. f. i.— 
Liasy Whitby. 
