160 AMERICAN JOURNAL 



shell undoubtedly, are quite as important as those which he 

 assigns to his Melanopidx. When we come to consider the 

 geographical distribution of the two groups, the reasons for 

 this separation are still more obvious. We find the Mela- 

 nopidse distributed over both hemispheres, while the Ceripha- 

 sinse are entirely restricted to North America, to the exclu- 

 sion almost entirely of the Melanojddce^ and totally of the fringe- 

 mantled Mela7iiidi£. We find them inhabiting this faunal 

 province in immense numbers of species, exuberantly varied 

 in form, size, weight and color, presenting a number of de- 

 scribed (and many undescribed) genera, — in fact, exhibiting all 

 that redundancy of character and isolation of position which 

 are the sure indications of a primordial separate existence* 



The publication of Mr. Gill's paper re-directed Prof. Ilalde- 

 man's attention to the subject, which he had left unfinished 

 in his investigations at an earlier period ; and the result is the 

 publication of a short but important paper in the Proceedings 

 of the Academy of Natural Sciences, September, 1863, en- 

 titled, "On StrepomatidcB as a Name for a Family of Fluviatile 

 Mollusca usually confounded with Melania," wherein he 

 finally separates our species as a distinct family, remarking 

 that the Oriental Melanians are not so nearly allied to ours as 

 they are to the Geritldadije, — with which conclusion we cordi- 

 ally agree. 



We have, therefore, adopted the name Strepomatidse as in- 

 dicating a distinct family, in preference to the prior name of 



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

 shells as a means of distinguishing generic and family groups, and to rely 

 wholly on such differences as may be found in the animals. Without deny- 

 ing the great importance which should properly be accorded to the latter, 

 we would insist that, in general, the expressioii of these differences may be 

 observed in the shell, and that at least very few generic distinctions have 

 been made from the study of the animals which have not been also indi- 

 cated plainly enough by the shell. The study of Malacology is yet in its 

 infancy, and those who figure in it are very apt to give undue importance 

 to the characters on which they rely for building up their systems. To in- 

 vestigate how many characters of form or function have successively been 

 called forthnslhe most important to stand godfathersat the baptisms of new 

 genera, would be curious, but lamentable. 



One thing is certain, that genera founded on the shells alone are alway.^ 

 found to be corroborated by the study of the animals, while many genera 

 founded on differences in the animal have remained unverified, 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 differences, so far as discovered, in the animals of 

 our so-called Melanians from the Oriental Melaniidw, as of sufficient import- 

 ance to justify their separation : We are contented to separate them upon 

 considerations connected with the shell only and with geographical distri- 

 bution, and accept the differences in the animals as merely corroborative, 

 for the present, believing, however, that other and more important distinc- 

 tive characters will reward the industry and skill of some future Malaco- 

 logist. 



