vm 



subfamily. " The American Melaniidce, so far as I 

 know, have not a fringed mantle, and, consequently, 

 belong to a difierent group." We readily admit the 

 propriety of separating the Ifekmojndw from Me- 

 InnlUJa', as a distinct family, and only wonder that 

 Mr. Gill did not make a famUy of Cerlphasince, 

 as the distinctive characters of the animal, so far as 

 known to us, and of the shell undoubtedly, are quite 

 as important as those wdiich he assigns to his Mela- 

 nopidce. When we come to consider the geograph- 

 ical distribution of the two groups, the reasons for 

 this separation are still more obvious. We find 

 the Melcmopidce distributed over both hemispheres, 

 while the Cer'q^hasinoe are entirely restricted to 

 North America, to the exclusion almost entirely of 

 the Melanopidce, and totally of the fringe-mantled 

 Melamidcti. We find them inhabiting this fiiunal 

 province in immense numbers of species, exuberantly 

 varied in form, size, weight and color, presenting a 

 number of genera — in fact, exhibiting all that redun- 

 dancy of character and isolation of position which 

 are the sure indications of a primordial separate 

 existence.* 



*It has become fashionable lately to disparage the value of the 

 mere, sh<;lls as a means of (iislingiiishing generic and family groups, 

 and to rely wholly on such diflerences as may be found in the animals. 

 Without denying the great importance which should properly be 

 accorded to the latter, we would insist that, in general, the expression 

 of these diflerences may be observed in the shell, and that at least 

 very few generic distinctions have been made from the study of 

 the animals which luive not been also indicated plainly enough by the 

 shells. The study of Malacology is yet in its infancy, and those who 

 tigure in it are very apt to give undue importance to the characters 

 on which they rely for building up their systems. To investigate how 

 many characters of form or function have successively been called 

 forth as the most important to stand godfathers at the baptisms of 

 new genera, would be curious, but lamentable. 



Que thing is certain, that genera founded on the shells alone are 

 always found to be corroborated by the study of the animals, while 

 many genera founded on differences in the animal have remained 

 unverilicd, and will continue so, owing to the undue importance given 

 to the difference of form relied on for the generic distinction. 



We do not regard the diflerences, so far as discovered, in the 

 animals of our so-called Melaniiins from the Oriental Melaniidx, as 

 alaiic of sufficient importance to justify their separation; we are con- 

 tented to separate them upon cousidcrations couuected with the shell 



