

GENUS HARPA. 5 



the contrary, does not exist ; this circumstance only, constitutes 

 the difference between them; whilst remote from them are 

 found other shells, possessing alike an analogous operculum, but 

 dissimilar to the first in every other respect. Thus the Harps 

 arid the Tuns have such striking resemblances to the BUCCINUM, 

 that we have always seen them placed near this last genus by all 

 authors who have described them ; nevertheless, the first two of 

 these genera have no operculum, whilst, on the contrary, it is 

 invariably found in the other. 



We may then infer, from these remarks, that the character 

 of the operculum cannot, as we have said, constitute a general 

 rule of classification. It will serve, with more certainty, for 

 some divisions of genera; and the differences of the opercula of 

 some shells may assist in establishing between them an accurate 

 measure of affinity or remoteness. 



The animals of the Harps appear to subsist upon soft and 

 delicate substances. Lamarck, in his Histoire des Mollusques, 

 has divided this genus into eight species ; but, after the example 

 of Deshayes, withdrew from the list of species the imperial 

 harp, which is only a pretty constant variety of the vcntricose 

 harp ; this may be proved by a specimen in the collection of the 

 prince Massena, which is half imperial harp by its very con- 

 tiguous ribs, and half ventricose harp by others more distant. 

 The conoid harp appears also to be only a variety of this last, 

 merely a little more elongated. The striated harp belongs also 

 to the ventricose harp, and should be considered as only a very 

 young specimen of this species. 



It is a general observation, that all the young shells of this 

 genus have longitudinal striae, more or less numerous, but al- 

 ways more approximate ; they have often, also, pretty apparent 

 transverse striae, distinctions easy to be observed in the shell of 

 which we have just spoken. 



The other species pointed out by Lamarck appear to be well 

 distinguished ; all agree in the common character of presenting 

 exteriorly parallel, compressed, inclined, and acute longitudinal 

 ribs ; in all, too, the upper extremity of each rib forms a small 

 detached sharp point. 



