232 TESTACEOUS MOLLUSCA. 



T. Crocea Lam. 4.— List. t. 253. /. 190.— Ch.f. AdG.—E. t, 

 235./. 2. Oval, longitudinally striated, somewhat saffron coloured, 

 particularly towards the margin, ribs narrow imbricated and scaly ; 

 scales numerous and most of them short but slightly raised at the 

 margin, posterior depression large. — Far. (Cham a Gigas var. C. 

 D. p. 214.— Gualt. t. 92. A.) Whitish. — 4. Indian Ocean. ..South 

 Seas ? 



T. Mutica Lam. 5. — Ast. t. 80. /. 1,2,3. Large, oval, ven- 

 tricose, ribs smooth but becoming scaly towards the margin, scales 

 depressed, interstices of the ribs longitudinally striated, posterior 

 aperture small, and the inner margin scarcely crenulated. — 14|. . 

 Indian Ocean. 



T. Serrifera. Lam. 6. — Chama Gigas var. D. D. p. 214. — 

 Ch.f. 497. — E. t. 235./. 3. Oval, ventricose, uniform white, the 

 ribs longitudinally striated and unarmed, except the extreme pos- 

 terior ones which have scales resembling the teeth of a saw : inter- 

 stices with strong longitudinal grooves, the ventral margin very 

 rounded, posterior gape very small. 4i. . 6. Indian Ocean. A 

 few small scales are sometimes seen on the anterior extremity. 



HIPPOPUS. 



Equivalve, regular, inequilateral and transverse ; lunula not gaping ; 

 hinge with two compressed unequal anterior inserted teeth, liga- 

 ment marginal and external. 



H. Maculatus. Lam. 1. — Sow. G. — Reeve, t. 98. f. 1. — Cha- 

 ma Hippopus. Lin. 1137.— D. p. 215.— Ch.f. 498, 9.— W. t. 9. 

 f. 2. — D. t. 236. f. 2. Transversely ovate, thick, heavy and ven- 

 tricose, white or yellowish with scattered purplish red spots ; some- 

 what scaly, ribbed ; posterior depression heart-shaped and oblique 

 Indian Ocean. 6. 



TRIBE MYTILACEA. 



Hinge with a subinternal marginal ligament, which is linear, very en- 

 tire, and occupies a considerable portion of the anterior margin ; 

 shell rarely foliaceous. 



MODIOLA. 



Subtransverse, equivalve, regular ; the posterior side very short ; beaks 

 nearly lateral and inclined to the shorter side ; hinge without teeth, 

 lateral and linear ; ligament placed in a marginal furrow, and 

 nearly internal ; a muscular impression which is sublateral, elon- 

 gated and hatchet-shaped. 



