228 



Chama — continued. 



unicornaria. . subimbricated, rough, with unequal, semierect, 



vaulted squamse ; base of the larger valve extended. 

 lamellosa. . ovate, rounded, transversely plicated, with pointed, 



fimbriated concentric, lamelliferous folds ; lamellae dentated 



. . Grignon. 

 calcarata. . orbiculate, with acute distant transverse folds ; the 



upper ones echinated in rays with very long canaliculated 



spines. 



Tridacna. 



pustulosa. . transversely fusiform, ribbed, waved, sprinkled with 

 numerous pustules ; lips of the lunule reflected. . Nor- 

 mandy. 



Modiola. 



subcarinata. . oblong, smooth, lower margin keeled ; upper 



curved inward. . Grignon. 

 tulipea. . oblong, windingly contracted upwards ; obsoletely 



keeled beneath ; scutellum of the beaks circumscribed with 



ribs. . Havre. 

 cordata. . oblong, subcordated beneath ; ribs at the beak, very 



tumid. 

 solenoides, . elongate, narrow, roundedly angulate, rather bowed ; 



forepart obliquely sulcated ; no keel. . ChaufFour. 

 IWiophagites. . long, straight, roundish beneath, thin ; upper 



part rather depressed. 

 Presumed fossil. 



Mytili. 



scapularis. . sub trigonal, ovatedly wedge-form ; forepart ob- 

 liquely rounded, margin sharp ; hindpart blunt, grooved 

 longitudinally, subdecussated. . Coulaines. 



margarifaceus. . oblong, thin, pearly, tumid, posteriorly forming 

 a longitudinal smooth rib ; longitudinal and transverse 

 strise. . England. 



Pinna. 



subquadrivalvis. . narrow, wedge-form ; subtetragonal ; dorsal • 

 angle of the valves slit. . Parma. 



Perna. 



maxillata. . trigonal, convexo-depressed, thick ; hinge very 

 broad, furrowed with numerous long sulciform teeth. . 

 Virginia. 



mytiloides. .ovato oblong, depressed, base pointed ; hinge oblique. 



Avicula. 



trigonata. . very small ; wing very oblique ; foreside subtrun- 



cated, with a bowed sinus. . Grignon. 

 phalcenacea. . small, wing very oblique, hinder ear longitudinally 



grooved. . Bourdeaux. 



