286 DESCRIPTION OF NEW 



striate, obscurely rayed, with distant lines of growth; posterior slope wide, very dark, 

 and with obscure rays; umbonial slope very obscurely angular; anterior cicatrices con- 

 fluent; posterior cicatrices confluent; dorsal cicatrices placed anterior to the cavity of the 

 beaks; palleal cicatrix scarcely perceptible; cavity of the shell rather deep and oval; 

 cavity of the beaks rather shallow and rounded; nacre white and iridescent. 



Remarks. — I have had several specimens of this species many years, and have had great 

 difficulty where to place it. It is nearest allied to A?i.flitviatilis, — a species which has a 

 most remarkably extended geographical range; but it seems to me to differ too much to 

 retain it in that species. It differs in being less transverse, in the beaks being more medial, 

 and in the epidermis being darker. It is also a little more enlarged on the umbonial 

 slope. Being always very desirous to keep the number of our species as limited as pos- 

 sible, I very often defer for years describing specimens as new, which I cannot place 

 satisfactorily with those already characterized. More recently, I have received from 

 Prof. Powell several specimens of the same characteristics, from Little Rock, and I think it 

 will be found by the naturalists of Louisiana and Arkansas, whence it comes, that the cha- 

 racters will be found constantly to differ enough to distinguish it from fltivialilis, which 

 flourishes more than any other Anodonta in the middle states. 



Anodonta Californiensis. PL XXV. Fig. 47. 



Testa subalatd, Ixvi, elliptic*}, sabliiJJa/d, postice rotundata; valvulis temtibiis; natibus minutis, ad apices 

 undulatis ; epidermide virido-olivaced, nilidd ; margaritd alba et iridescente. 



Shell subalate, smooth, elliptical, somewhat inflated, rounded behind; valves thin, beaks very small and 

 undulated at the tips; epidermis olive-coloured, shining; nacre white and iridescent. 



Hab. Rio Colorado, California, J. L. Le Conte, M. D. 

 My cabinet and cabinet of Major Le Conte. 

 Diam. .8, Length 1.3, Breadth 2.2 inches. 



Shell subalate, smooth, elliptical, somewhat inflated, rounded behind, slightly compressed 

 towards the anterior basal margin; substance of the shell thin and fragile, beaks very 

 small, scarcely rising above the dorsal line, finely undulate at the tip; ligament rather 

 short and thin; epidermis virido-olivacea, shining, with rather distant marks of growth; 

 posterior slope rather broad, compressed and raised nearly into a wing, with three dis- 

 tinct green rays from the beak to the margin; umbonial slope inflated and rounded; 

 anterior cicatrices distinct; posterior cicatrices confluent; dorsal cicatrices nearly in the 

 centre of the beaks; palleal cicatrix scarcely visible; cavity of the shell rather deep; 

 cavity of the beaks exceedingly shallow; nacre white. 



Remarks. — Dr. Lc Conte procured but two or three specimens of this, which was the 

 only species of the family Naiades he saw in California. This marks a very singular dif- 

 ference in the existence of these forms of animal life, from those in the waters of the more 

 eastern states, where they exist in such profusion, and in such a great number of various 

 forms and habits. This species is more nearly allied, indeed it is closely allied to An. Nut- 

 lalliuna, which I described many years since, and which was brought by Mr. Nuttall from 



