84 DESCRIPTIONS 01' 



larger and not so transverse. In outline it is near to corrugatus, Lam., but being a 

 sulcate species cannot be for a moment confounded with it. The furrows are close 

 and well impressed on the anterior and but slightly on the posterior portion. They 

 diminish in size towards the beaks, where they are fine and close, but cease where 

 three or four small undulations exist at the tips. It is greatly to be regretted that 

 we have not the soft parts and more specimens to make a more perfect diagnosis of 

 this interesting little species. I owe this specimen to the kindness of Dr. Ruschenberger. 



Unio rudtjs. pi. 43, fig. 146. 



Testa Isevi, elliptica, crassa, inflata, inaequilaterali, posticfe emarginata, antice obliqu^ rotundata ; valvuHs 

 vald6 crassis, antic^ crassioribus ; natibus crassis proininentibusque ; epidermide tenebroso-fusca, 

 asper^ striata, radiis incisis ; dentibus cardinalibus parviusculis, sublongis, striatis, crenulatis, in 

 utroque valvule duplicibus ; lateralibus sublongis, subcrassis, granulatis curvisque ; raargarita alba 

 et paulisper iridescente. 



Shell smooth, elliptical, thick, inflated, inequilateral, emarginate behind and 

 obliquely rounded before ; valves very thick, thicker before ; beaks thick and promi- 

 nent; epidermis dark brown, roughly striate, with indented rays; cardinal teeth 

 rather small, somewhat elongate, striate, crenulate and double in both valves ; lateral 

 teeth somewhat long, rather thick, granulate and curved; nacre white and slightly 

 iridescent. 



IMo rud^ts, Lea. Proc. Acad. Nat. Sci., 1859, p. 187. 



Hah. — Rio de la Plata, South America. G. Von dem Busch, M. D. 



My cabinet and cabinet of Dr. Von dem Busch, Bremen. 

 Diam. 1-4, Length 2-2, Breadth 3 inches. 



Shell smooth, elliptical, thick, inflated, inequilateral, emarginate behind, obliquely 

 rounded before ; substance of the shell thick and ponderous, thicker before ; beaks 

 thick and prominent ; ligament rather short, thick and light brown ; epidermis dark 

 bi'own, lighter towards the beaks, roughly striate, the marks of growth being rather 

 close and irregularly impressed into furrows, which are crossed by a few indistinct 

 impressed furrows from the beaks to the margin ; umbonial slope raised and rounded ; 

 posterior slope broad, rather flat, with a low keel rising from a deep broad furrow ; 

 cardinal teeth rather small, somewhat elongate, striate, crenulate and double in both 

 valves ; lateral teeth somewhat long, rather thick, granulate, thickened towards the 

 end and curved ; anterior cicatrices distinct, large and deeply impressed ; posterior 

 cicatrices confluent, rather large and well impressed ; dorsal cicatrices well impressed 

 and placed in a row across the centre of the cavity of the beaks ; pallial cicatrix 

 irregular and deeply impressed ; cavity of the shell deep and rounded; cavity of the 

 beaks rather deep and subangular; nacre white, disposed to be pinkish at the anterior 

 basal margin and iridescent. 



Remarhf. — There was a single specimen only of this species sent to me by Dr. 



