6S 



SHELLS AND SHELL-FISH. 



authors is more a murex than a purpura^ — that Triton 

 passes into Buccinum, and therefore represents it, — and 

 that, of all the carnivorous gastropods out of the Cassince, 

 Murex Magellanicus and its allies have the greatest 

 similarity to the harp-shells. This is all we would 

 maintain. For the rest, there is such an extreme regu- 

 larity in all the existing species of Harpa, that we may 

 fairly conclude the aberrant examples have become 

 extinct, or have possibly not been discovered. One 

 species, however, of Muricidea, with the ridges of 

 M. Magellanica, but with a truncated base, would con- 

 nect the two groups ; and when we consider that, in 

 Triton, the comparative length of the channel is only 

 used to designate the species, we may fairly conclude 

 there is no violation of nature in supposing that Harpa 

 and Muricidea pass into each other. As for the analogy 

 between the latter and Nassa, we have at this moment 

 a species of Muricidea before us, whose canal is 

 reflected backwards precisely as in the common iV. ar- 

 cularia. 



(^5^.^ The typical distinction of the Nass^ lies in 

 a very thick deposition of enamel which encircles the 

 aperture, and not only spreads far beyond the inner lip, 

 hut forms a vitreous mass all over the under part of 

 the body-whorl. The only other genus of predaceous 

 Testacea having a shell thus constructed, is Cassis, and 

 a few tritons, which are probably its representatives. 

 Nevertheless, there are many Nassce which have this 

 peculiarity but slightly developed, and others in which 

 it is not at all apparent ; in all, however, there is a pro- 

 minent internal ridge at the base of the pillar, and a 

 small transverse tooth on the upper part of the inner 

 lip. These shells are all of a small size, and abound 

 in the shallow waters of Southern Europe and the East. 

 Among the unpublished researches of Guilding*, is a 

 highly finished drawing of a species from St. Vincent's 

 (fig. 2.), which throws an important light on the animal : 



* Now in the possession of his widow. 



