a 



I 



JUKES-BROWNE : ON CALLISTA, AMIAKTIS, AND PITARIA. 345 



curving forward. Right anterior cardinal pointing to lower anterior 

 lateral, posterior broadly bifid. Pallial sinus deep, ascending. This 

 group is Cretaceous and Eocene, including C. fiitidula, Lam., C. nitida, 

 Desli., C. tra7iquilla, Desh., and C. corhulina, Desh. 



Lepidocardia, Dall, 1 902, Type, Venus Africana, Phil. ( =jioridellay 

 Gray). 



Shell ovate, compressed, posteriorly attenuated, nearly smooth, but 

 showing radial strife. Hinge-plate sliort, with crowded teetli, the 

 left anterior lateral long and reacliing nearly to top of anterior 

 cardinal. Pallial sinus horizontal, pointed. No other species 

 known. 



Transenella, Dall, 1883. Type, T. Conradina, Dall. 



Shell oval or sub-trigonal, smooth or striate. In left valve three 

 divergent cardinals, the median being thick and triangular ; in right 

 valve the anterior is short and undercut, the posterior narrow and 

 often entire. Pallial sinus rounded. Valve-margins tangentially 

 grooved. This includes C. pannosa, Sow., C. puella, Carp., and 

 C. angulifera, Sow., besides the species mentioned by Dr. Dall, and 

 there are also some species of Miocene age. 



Tivelina, Cossmann, 1887. Type, C. teUinaria, Lam. 



Shell small, oval, compressed and posteriorly attenuated; surface 

 smooth or finely striate ; hinge-plate strong in front, but curtailed 

 behind ; cardinal teeth all short ; left valve with a strong anterior 

 lateral and three divergent cardinals, of which the median is triangular 

 and the posterior narrow and contluent with nymph ; in the right 

 valve the pit of the anterior lateral is sometimes isolated, sometimes 

 continued into a channel which undercuts the anterior cardinal. 

 Pallial sinus small, rounded, and ascending. 



Genus Amiantis, Carpenter, 1863. 



Type, Cijtherea callosa, Conrad (= Diane nobilis, Sow.). 



Synonyms: Dione {in part), Gray; Dione, Riimer; Jlysteroconcha, 

 Lang (in Fischer), pre-Linncean. 



Shell oval, more or less angulated on the posterior slope ; surface 

 sculpture of concentric ridges ; luuule impressed and circumscribed, 

 escutcheon defined, but vei'y narrow, with raised ligamental margins ; 

 ligament long, open, and conspicuous ; hinge similar to that of Callista, 

 but in the left valve the pit between the anterior laterals is continued 

 into a channel wliich passes under the anterior cardinal ; left median 

 thick and triangular, right median semilunar; nymphs rugose or 

 longitudinally grooved ; pallial sinus deep and horizontal. 



In Amia7itis (s.s.) the shell is thick, oval, glossy, and strongly 

 ribbed ; the interior is irregularly thickened ; the hinge is thick, the 

 right posterior cardinal grooved, the left one long and prominent ; 

 nymphs rugose ; pallial sinus linguiform and pointed. Only two 

 recent species are yet known, A. callosa, Conr., and A. purpurata, 

 Lam., but it is represented in the Miocene of Aquitaine by Cytherea 

 undata, Bast. 



Section Lamelliconcha, Dall. Type, C. concinna, Sow. 



Shell oval, striated or ridged ; hinge-plate excavated and attenuated 



