OP CONCHOLOGY. 129 



Lamarck's name Pterocera having been the first one proposed 

 that was binomial and accompanied by a diagnosis, must therefore 

 be adopted ; and as it was especially typified by P. lambis, it 

 must be retained for the group represented by that species. 



Having repeated the diagnoses of the several subdivisions of 

 Pterocera proposed by authors, it will be apparent that none have 

 been hitherto based on more than the number of spines and the 

 absence or presence of labial rugosities. It may further be re- 

 marked that previous authors have equally failed in their spe- 

 cific descriptions or otherwise to recognize any other than numeri- 

 cal differences, or those of form in the digitations. 



With respect to the subdivisions of tlie Lamarckian genus, 

 Morch, first of the moderns who subdivided it, gave no diagnoses, 

 and, if he should be judged by his distribution of the species, it 

 would be diSicult to surmise his views ; but, as already remarked, 

 his chief error was probably typographical or inadvertent. 



The diagnoses of the Adams brothers are not consistent with 

 the contents of the genera, two of the five species of Blillipes 

 { ]jse2ido-scorjno and Scorpio) not having the " digitations of outer 

 lip numerous," but "not numerous," as in Heptadactylus^ from 

 which they diff"er, however, by having the "outer and inner lips 

 corrugated." The typical species of Harpago have the outer and 

 inner lips corrugated, and digitations not numerous ; consequent- 



tences. But would not the spirit of the rule cited require that the diag- 

 nosis should also, besides being correct in its original application, be even 

 strictly applicable to the groups with which the name should afterwards 

 be associated ? Little consideration would be sufficient to show what 

 confusion would be the result of such interpretation, however. In the 

 group under review, for example, the Linnsan diagnosis of St r ambus is 

 inapplicable to any group to which an author would now apply the name ; 

 Pterocera, as characterized by Lamarck, is quite different from that now 

 characterized, and still more apposite are the Adamsian diagnoses of 

 Harpago, Millipes, and Pterocera. The diagnoses of those groups (in one 

 case by implication) are by no means characteristic of their contents. The 

 diagnoses are simply transmutations in combination of two characters ; 

 that of J/^7/i'pes really excludes two of the five species referred to. and 

 those two would be relegated to Harpago I In this case the authors were 

 more happy in their appreciation than in their verbal limitation. The 

 question naturally recurs then, is a diagnosis that is actually erroneous, 

 and that misleads better than none at all ? But if we reply in the nega- 

 tive, and yet accept the rule, how many rejections of accepted names, and 

 what countless changes would the logical application of such a rule en- 

 tail ! The rule, however, has the merit of conveying the sense of natural- 

 ists generally, that one has no right to shirk a duty, even should he fail, 

 and that if his time be insufficient, or his power of expression be not ade- 

 quate to those of appreciation, silence should be his course, unless he 

 can make arrangement with another tu^V^m^ to assume the labor he is un- 

 able to perform. He, or a recognised representative should, at least, with 

 a new name, reveal the knowledge of which it may be supposed to be the 

 expression, — or perhaps, the ignorance. 



