374 MOLLUSCA. ACEPHALA. Spirifer. 



71. T. hemisphmrica. — Hemispherical, with a produced incurved beak, Ion- 

 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. dxxxvL f. 2. — In Chalk. 



73. T. striatula Imperfectly bilobate, compressed, longitudinally ovate 



and striated ; b front truncated, sometimes with a sinus ; striae granulated, re- 

 peatedly forked.— Mant. Geol. Suss. 131. t. xxv. f. 7, 8, and 12. Sower. Min. 

 Conch, t. dxxxvL f. 3, 4, 5. — In Chalk. 



74. 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. G, 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. Dxxxvii. 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 subcorneal, with 

 a straight beak, which is flat in the front — Soiver. Min. Conch, t. Dxxxvii. — 

 In Green Sand. 



77. T. Gibbsiana Suborbicular, rather triangular, ventricose, with 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. Dxxxvii. f. 4.— In Green Sand. 



78. Mantelliana.— Transversely obovate, gibbose, plaited; plaits 10, sharp, 

 front elevated with 4 to 6 plaits ; beak prominent but small. — Sower. Min. 

 Conch, t. Dxxxvii. 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 filling the shell. 



1. S. Giispidatus Apex of the perforated valve broadly truncated, forming 



a flat triangular space, the base of which is in the hinge, longitudinally rib- 

 bed with 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. exx and t. cccclxi. f. 2. — In Carboniferous Limestone. 



2. S. trigonalis. — Gibbose, transversely striated, with about twenty-six ra- 

 diating sulci ; hinge-line as long as the shell is wide ; front semicircular ; 

 the three central ridges elevated ; beaks incurved, approximating. — Ano- 



mise striata, Ure, Ruth. 314. t. xv. f. 1 An. trigonalis, Mart. Derb. t. xxxvi. 



f. 1 Spir. trig. Sower. Min. Conch, t. eclxv. — In Carboniferous Limestone. 



3. S. triangularis " Differs from S. trigonalis principally in the sides being 



direct or si might, not rounded, forming acute angles with the hinge; and, 



