OF CONCHOLOGY. 87 



3. Shell delicate and pellucid, striae not perceptible, beaks 

 calyculate ; example Sph.2'>ci7'tu'meiuvi; Sj^h. lacustre o? ^nro\)e. 



4. Shell very small, delicate, transverse, striae very light, 

 beaks calyculate ; example Sph. Bahiense ; SpJi. Africmiwn of 

 South Africa." 



Following the preface is a Systematic Index of the species 

 described, amounting to one hundred and eleven, including the 

 fossil ones. Of these, thirteen, principally South American, be- 

 long to the genus Corhicula ; there are thirty-six species of Cy- 

 rena, of which two or three recent, and two fossil species are 

 found in the United States, the rest in Mexico, Central and 

 South America and West Indies ; of Sphaerium there are forty- 

 four species, nearly all natives of the northern United States; 

 and, finally, Pisidium contains eighteen species, with the same 

 distribution. 



The following species are described for the first time : — 



Corhula perplexa, South America. 

 Cyrena regalis, South America ? 

 " or dinar ia, " ? 



" coJorata, Island of New Providence, West Indies. 

 Splicermm contractum, i^labama. 



" parouhtm, Porto Rico, W. I. 

 " viridante, Morelot, Gaudeloupe, W. I. 

 " Cubense, Cuba. 



Pisidium simile, Gaudeloupe, W. I. 



" uUramontanum, Canoe Creek, California. 

 " consangiiincum, Cuba. 

 The name of Cyrena tumida is substituted for C. angulata, 

 Deshayes, (preoccupied). 



The illustrations of the species (wood engravings) are excellent- 

 and all that could be desired for the purposes of identification, 

 We cannot close this notice without deprecating the too prevalen. 

 practice, which Mr. Prime has followed, of quoting for the spet 

 cies the name proposed for it by the first author who placed it in 

 the genus to which it is now referred. The consequence of this is 

 that, in several cases, old and well-kno"wn specific names are cast 

 aside and others substituted. Besides the manifest injustice thus 

 committed towards the discoveier of the species, this principle is 

 gravely faulty, in substituting for one permanent specific name 

 an appelation that must ever change with each change in our 

 ideas of classification. Genera as understood by scientific men 

 are eminently artificial, and therefore can have no permanent 

 limits, but are liable to be divided and combined in various ways 

 according to the views we take of them ; shall we then lose the 

 only sign-post by which to recognize a species, by changing its 



