III.-. 



monogkaph of the family 

 NUCULIDyE, 



FORMING THE LAMARCKIAN GENUS NDCULA. 

 By Sylvanus Hanley, F.L.S., etc. 



The essential ideal of a Lamarckian Nitcula — 1 do not mean 

 the genus according to the precise definition of Lamarck, for that 

 would scarcely include even the few shells he lias indicated, but 

 Nucula so extended as to comprehend all the species which that 

 author, when he finally elaborated his system, would have linked 

 together, had he known them — is a bivalve hinged by a series of 

 comb-like teeth. Thus simply characterized, its members form an 

 easily recognizable assemblage, which, however, the exigence of 

 modern classification compels us to subdivide as naturally as mav 

 be. 



The empirical school of conchologists, which prefers the arbi- 

 trary selection of a strongly characterized type, and the grouping 

 around it of such shells as resemble it in general aspect, to a strict 

 generic definition (in default of which a species may be adjudged, 

 even by an adept, to more groups than one), has distributed the 

 pristine Nitcula into six genera or subgenera {Nucula proper, Leda, 

 Yoldia, Portlandia, Solenella, Neilo), placed far apart by D'Or- 

 bigny, and certain other naturalists, in different families. Without 

 arrogating to myself the skill to decide upon the rank, position, 

 and value of these sections, I have preferred to follow the more 

 moderate views of Woodward, because, while nothing is easier 

 than to discriminate between a nacreous Nucula proper, a porcel- 

 lanous Leda without a prominent ligament, and a porcellanous 

 Solenella with one, no adequate and universal characters by which 

 all the Yoldia and Portlandia may be indisputably distinguished 

 from all the Leda have ever been indicated. The published de- 

 finitions are either inapplicable to all, or would comprehend several 

 undoubted licda. 



VOL. III. M 



