884 PROCEEDINGS OF THE NATIONAL MUSEUM. VOL.XX. 



This division was proposed for those species which have a short ros- 

 trum, defined by a radial ridge and a furrow. The type has a well- 

 marked dorsal ligamental furrow and a small notch or "socket" under 

 the beak for the specialized part of the ligament. It is uncertain, 

 whether it has a siphon and a pallial sinus. In case these are present, 

 it should form a distinct genus and be placed under Malletinse. 



ANALYTICAL TABLK OF RECENT SUBFAMILIES, GEXEKA, AND SUBGENERA OF LEDID.E 



AND XUCULID.E HERE ADOPTED. 



A. Shell not gaping, short-ovate, subtrigonal, or rounded; posterior end without a 

 rostrum; beaks usually curved backward; no siphon tubes nor pallial sinus. 



Xuculidw d'Orbigny. 



B. Shell more or less trigonal, usually oblique; posterior end usually shorter; 

 beaks turned backward Nnciilitue Verrill and Bush. 



c. Teeth numerous, transverse, V-shaped, forming two convexly arched or augu- 

 lated series; a distinct median chondrophore; no lateral teeth. 



yucula Lamarck, 

 cc. Teeth few, not forming long series; a long lateral tooth in each valve; uo 



median chondrophore Nticitlina d'Orbigny 



AA. Shell ovate, oblong or lanceolate; posterior end generally the longer and 

 usually more or less rostrated; siphon tubes and pallial sinus generally present. 



Lt-didiv H. and A. Adams. 



C. Cartilage or resilium present, not closely united with the external ligament. 



Ledinw H. and A. Adams. 

 a. Resiliuui supported by a definite concave chondrophore extending inward to, 



or beyond, the inner edge of the hinge-plate. 

 li. Shell not gaping unless at the end of the rostrum. 

 o. Shell distinctly rostrated and carinated posteriorly. 



Leda Schumacher (sense extended). 



d. Shell elongated and tapered posteriorly, rostrum long, bicarinate, blunt ; liga- 

 mental area or escutcheon long and well-defined; pallial sinus and siphon 

 tubes developed Leda (sense restricted ). 



dd. Shell shorter, swollen, ovate or oblong, posteriorly not much elongated; ros- 

 trum short, usually acute, unicarinate. 



e. Shell ovate, rostrum small, acute; ligamental area or escutcheon distinctly 

 bordered by a carina. 



/. Rostrum short, subacute, submediau, denned below by a ventral sinuosity or 

 emarginatioii Junonia Seguenza ZedeZ/a Verrill and Bush. 



ff. Rostrum short, dorsal, not defined below by a ventral sinuosity; postero- 

 dorsal margin concave; escutcheon -sunken Jiiplteria Bellardi. 



ee. Shell oblong, angular, subtruncate, rostrum short, angular, dorsal, defined 

 below by a marginal sinuosity; escutcheon well-defined Fortlandia Morch. 



ccc. Shell not rostrated, small, ovate or elliptical, rounded at both ends, anterior 

 end the shorter, no carina, luuule, nor escutcheon; cartilage posterior, inter- 

 nymphal Microyohlia Verrill and Bush. 



Ib. Shell oblong or lanceolate, compressed, nearly plain, more or less gaping at 

 both ends ; rostrum not well-defined ; pallial sinus large and broad ; tubes long, 

 united. 



r/. Teeth transverse, -shaped, numerous, in two long series; chondrophore large, 

 concave, projecting strongly inside the hinge-plate. 



YoJdia Miiller (sense extended). 



h. Shell large, compressed, rounded anteriorly, broadest posteriorly with apostcro- 

 ventral protrusion and radial ridge; rostrum short, broad, poorly defined; 

 external ligament well developed, prominent both sides of the beaks, occu- 

 pying a continuous furrow; no lunule nor escutcheon. 



Megayoldia Verrill and Bush. 



