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 
and 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 ventricose 
harp ; this may be proved by a specimen in the collection of the 
prince Massena, which is half zmpertal 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 striz, 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. 
