22 



UNIO SILIQUOIDEUS. 



"'Plate X. Fig. 1. 

 DESCRIPTION. 



Shell ovate-oblong or elliptical, ventricose, mode- 

 rately thick; surface glabrous, olive-yellow, with nu- 

 merous green rays varying much in size; anterior 

 side not very short, margin regularly rounded; liga- 

 ment margin straight, not declining; posterior ex- 

 tremity angulated; umbonial slope undefined; beaks 

 with flexuous undulations; within bluish-white; cardi- 

 nal teeth oblique, lateral teeth slightly decurved pos- 

 teriorly. 



SYNONYMES. 



U. siLiquoiDEus, Barnes. Silliman's Journ. vol. vi. p. 269. 

 U. inflatus, lb. p. 267. 

 Cab. Jl. N. S. No. 1055. 



OBSERVATIONS. 



The species which most resembles this appears to 

 be the radiatus, which for comparison we figure upon 

 the same plate. Young specimens differ constantly 

 from the radiatus in having a straw-coloured highly 

 polished epidermis, and much undulated beaks; are 

 more inflated, have the anterior side longer and the 

 margin more regularly rounded. The sexual varie- 

 ties are far more strongly marked, some specimens 

 having almost the form of U. cariosus, whilst the ra- 

 diatus offers comparatively slight differences of out- 

 line. Old shells become thick and much inflated, and 



