72 • DESCRIPTIONS Of 



of the cavity of the beaks ; cavity of the shell rather deep and rounded ; cavity of the 

 beaks shallow and obtusely angular ; nacre white and iridescent. 



Remarlis. — Like many other species from Mr. Cuming, there was only a single 

 specimen of this. This is always to be regretted, as the individuals of this genus vary 

 so much. In this case the epidermis of one of the valves is bleached, and therefore 

 very different in color from the other. The radiating undulations of the beaks show 

 the South American type. In outline it is near to merus, (nobis), and Mexicamis, 

 Phili., but is a little more transverse than either and much smaller than the former. 

 It is not so square as modestus, Fer., nor is it so much compressed. 



Unio diminutus. pi. 39, fig. 134. 



Testa plicatS,, corrugata, subsulcata, elliptica, insequilaterali, compressa, postic5 obtuse angulata ; valvulis 

 crassiusculis ; natibus subprominentibus, ad apices undulatis acuminatisque : epidermide lutea eradia- 

 taque: dentibus cardinalibus parviusculis, compressis, erectis, crenulatis, in utroque valvulo dupli- 

 cibus ; lateralibus subbrevibus rectisque ; margarita pallido-salmonia et iridescente. 



Shell plicate, shrivelled, somewhat sulcate, elliptical, compressed, inequilateral, 

 obtusely angular behind ; valves somewhat thick ; beaks rather prominent, undulated 

 and pointed at the tips ; epidermis yellow and without rays ; cardinal teeth rather 

 small, compressed, erect, crenulate and double in both valves; lateral teeth rather 

 short and straight ; nacre pale salmon color and iridescent. 



Unio diminutus, Lea. Proc. Acad. Nat. Sci., 1859, p. 151. 



Hah. — East Africa. H. Cuming and Prof Hanley. 



Cabinets of Mr. Cuming and Prof. Hanley. 

 Diam. 4, Length -8, Breadth 1-3 inch. 



Shell folded, shrivelled, somewhat sulcate, elliptical, inequilateral, compressed, 

 obtusely angular behind ; substance of the shell somewhat thick ; beaks rather promi- 

 nent, undulated and pointed at the tips, the undulations forming an acute angle in 

 the middle ; ligament very small and yellowish ; epidermis straw yellow, without rays 

 and somewhat shining ; umbonial slope slightly raised and rounded ; cardinal teeth 

 rather small, compressed, erect, crenulate and double in both valves; lateral teeth 

 rather short and straight; anterior cicatrices distinct and well impressed; posterior 

 cicatrices confluent ; dorsal cicatrices on the plate vrithin the cavity of the beaks ; 

 cavity of the shell rather shallow; cavity of the beaks rather shallow and angular; 

 nacre pale salmon color, satin-like and iridescent. 



Remarks. — The two specimens before me of this small and interesting species are 

 all I have ever seen of it. That from Mr. Cuming is very perfect and nearly double 

 the size of Prof Hanley's, which is evidently a young individual. The corrugate and 

 shrivelled appearance of the surface is occasioned by transverse furrows which meet 

 with the small folds and cut them abruptly. These furrows are well characterised on 



