﻿DROMUS 



341 



Genus DROMUS Simpson, 1900. 



Dromtis Simpson, Syn., 1900. p. 614. — ^>rtmann, Ann. Car. 



Mus.. VIII, 1912, p. 314. 



Shell solid, roinided-triang-ular ; beaks well forward, rather 

 high : beak sculpture consisting- of fine ridges running parallel 

 with the growth lines, the furrows between the ridges inter- 

 rupted at the posterior ridge ; posterior ridge distinct ; a series 

 of humps runs from the beaks down to the central part of the 

 base of the shell, wdiich is otherwise sculptured bv irregular, 

 concentric ridges ; epidermis beautifully painted by undulated, 

 radiating, broken hair lines or fine maculations ; hinge plate 

 wide and flat ; pseudocardinals triangular, small and low, rag- 

 ged ; laterals low, short, club-shaped : cavity of the beaks deep 

 and compressed, dorsal muscle scars on the under side of the 

 hinge shelf; adductor scars small ; front part of the shell very 

 thick, suddenly liecoming thinner at the row of humps ; male 

 and female shells much alike. 



Animal with the inner branchire much the larger, curved be- 

 low, free from the abdominal sac ; marsupium occu])ying the 

 base of nearly the whole outer branchise in numerous, rather 

 indistinctly marked ovisacs, bases of the ovisacs slightlv round- 

 ed ; ova verv minute: palpi small, curved; branchial opening 

 very large, extending one-third of the way along the base, 

 fringed with many brown papill?e ; anal opening very large, 

 finely crenidated. 



Type, Unio dramas Lea. 



Dromus DROMAS (Lea). 



vShell subtriangular or subelliptical. inflated, solid, somewhat 

 inequilateral, with full, high beaks, whose sculpture consists 

 of fine ridges running parallel with the growth lines, the fur- 

 rows interrupted at the posterior ridges ; surface with irregular, 

 concentric growth lines or ridges, with a decidedly strong con- 

 centric ridge around the earlier growth of the shell. This ridge 

 is raised into a heavy irregular knob or hump about on the 

 median line of the shell and sometimes there is a curved row 



