1846.] 



MORRIS ON TEREBRATULA; 



387 



within the deltidial area, and more or less separated from the hinge- 

 line by the deltidium or open below. Shell punctated or non- 

 punctated. 



The genus is divided into two sections, EpithyridcB and Hypo- 

 thyridce, 



Epithyridce. 



Beak truncate, a circular or oval perforation above the deltidial 

 area, either entire and surrounded principally by the dorsal valve, 

 or a round opening in the dorsal valve more or less bounded at the 

 sides by the deltidium. Shell punctated. 



Group 1. Plicate. 

 1. Dichotomy. 



a. Cost at ee. 

 T. orbicularis, Sow. 



(T. cardium, Lam.) 

 T. oblonga, Sow. 

 T. Adrieni, De Vem. 



p. Striata. 

 T. substriata. 

 T. striatula. 

 T. Defrancii. 



T. chrysalis. 



T. Toreno, De Vem. 



y. Rostrat(B. 

 T. lyra, Sow. 

 T. pectita, Sow. 

 T. rostrata, Defr. 



S. Expansce. 

 T. truncata. 

 T. detruncata. 



Loricatae. 

 T. coarctata. 

 T. loricata. 

 T. ferita. 

 T. Menardi. 

 T. Sayi. 



Group 2. NON-PLICATJE. 

 2. CoSTATiE. 



Cinctae. 

 T. trigonella. 

 T. quadrifida. 

 T. numisraalis. 

 T. digona. 

 T. lagenalis. 

 T. comuta. 

 T. diphya. 

 T. hastata. 



3. L^vES. 



Jugatge. 



a. Repandee. 

 T. carnea. 

 T. semiglobosa. 

 T. longirostris. 

 T. elongata. 

 T. ornithocephala. 

 T. vulgaris. 



j3. Excavatce. 

 T. sufflata. 



Carinatae. 



a. Sinuata. 

 T. biplicata. 

 T. perovalis. 

 T. ampulla. 

 T. Ilarlani. 

 T. globata. 



j3. Acuta*. 

 T. impressa. 

 T, resupinata. 

 T. carinata, Lam. 



HypothyridcB. 



Beak acute, perforation below the beak and within the deltidial 

 area; entire, and nearly surrounded by the deltidium, or not (Mitire 



