374 
MOLLUSCA. ACEPHALA. 
Spirifer. 
71 . T. hemisphcsrica. — Hemisphserical, with a produced incurved beak, lon- 
gitudinally striated ; striae very numerous — Sower. Min. Conch, t. cccxxxvi. 
f. 1. — In Oolite. 
72 . T. rigida. — Orbicular, plaited ; plaits granulated, increasing in number 
towards the margin ; lesser valve nearly flat, the other convex. With a small 
beak. — Sower. Min. Conch, t. Dxxxvi. f. 2. — In Chalk. 
73 . T. Imperfectly bilobate, compressed, longitudinally ovate 
and striated ; j^front truncated, sometimes with a sinus ; striae granulated, re- 
peatedly forked. — Mant. Geol. Suss. 131. t. xxv. f. 7? 3, and 12. Sower. Min. 
Conch, t. Dxxxvi. f. 3, 4, 5 — In Chalk. 
T4. T. pisum. — Suborbicular, rather square, thick, depressed^ plaited ; plaits 
numerous, simple, sometimes granulated ; front slightly elevated, beak small, 
incurved — Sower. Min. Conch, t. Dxxxvi. f. 6, 7*^ — In Chalk Marl. 
75 . T. rostrata.— Suborbicular, gibbose, plaited ; plaits many, rounded ; 
beak large, produced, slightly incurved, pointed ; front slightly elevated. — 
Sower. Min. Conch, t. nxxxvii. f. 1, 2. — In Chalk Marl. 
76. T. truncata. — Semicircular, plaited ; plaits sharp, from 9 to 20, some of 
them forked ; front elevated with from 1 to 5 plaits ; hinge-line straight, equal 
to the width of the shell ; lesser valve nearly flat, the other subconical, with 
a straight beak, which is flat in the front. — Sower. Min. Conch, t. nxxxvii. — 
In Green Sand. 
77* T- Gibbsiana — Suborbicular, rather triangular, ventricose, vdth nume- 
rous rounded, simple plaits ; front much elevated, with about 10 or 12 plaits, 
flattened ; beak small, incurved, pointed ; small valve most convex — -Soiver. 
Min. Conch, t. nxxxvii. f. 4. — In Green Sand. 
78. Transversely obovate, gibbose, plaited ; plaits 10, sharp, 
front elevated with 4 to 6 plaits ; beak prominent but sm 2 li.<>-^Sower. - Min. 
Conch, t. nxxxvii. f. 6 — In Chalk Marl. 
Besides the above extended list of extinct species (of which not a few will 
probably be found to be varieties), there are indications of a few other species 
in the writings of British geologists ; but too obscure to warrant their inser- 
tion here. 
Gen. SPIRIFER. — Hinge transverse ; perforation for the 
ligament triangular, in a longitudinal flattened space un- 
der the beak ; two spirally coiled linear appendages to 
the hinge, nearly Ailing the shell. 
1. S. cuspidatus.—Ajpeyi of the perforated valve broadly truncated, forming 
a flat triangular space, the base of which is in the hinge, longitudinally rib- 
bed Avith a broad mesial furrow ; the other valve ribbed, with a mesial ridge. 
— Anomia cusp. Mart. Linn. Trans, iv. 45. t. hi. — Spir. cusp. Sower. Min. 
Conch, t. cxx and t. cccclxi. f. 2. — In Carboniferous Limestone. 
2 . S. Gibbose, transversely striated, with about twenty-six ra- 
diating sulci ; hinge-line as long as the shell is Avide ; front semicircular ; 
the three central ridges elevated ; beaks incurved, approximating. — Ano- 
mim striata, t/i'c, Iluth> 314. t. xv. f. 1. — An. trigonalis, Mart. Derb. t. xxxvi. 
f. 1. — Spir. trig. Soiver. Min. Conch, t. cclxv — In Carboniferous Limestone. 
3. S. triangularis — Differs from S. trigonalis principally in the sides being 
direct or straight, not rounded, forming acute angles Arith the hinge ; and, 
