Genus Latirus. 379 



my mind, raise the question of generic distinction on that 

 score alone. In a more or less undeveloped state, signs of 

 such a tooth appear on many shells. The shell is almost 

 more noteworthy on account of its bold sculpture, squarrose 

 aperture, and transverse thread-like marking on the whorls, 

 and I revert to it more fully in another part of this paper. 



The PeristerniincB were separated from the Latiri by 

 Morch, principally on account of the want of umbilicus, 

 moderate and narrowed canal, and slighter plications of 

 the columella, but there are many species which, pending 

 the working out of the dentition, must be doubtfully placed 

 in either genus. P. Caiedoitica (Crosse) is an undoubted 

 Perzsterniay but 1 have a specimen with a decided umbilicus ; 

 P. annulata (Bolten), allied to P. flavida and P. infracmcta^ 

 is, perhaps, better placed in Latirus^ near L. Syracusamis 

 (L.j, and so on. 



The species are nearly all small, and highly coloured, 

 especially as regards their mouths and columella; and their 

 form is more like the Nassce or Nassarice than is Latirus,^ 

 which more assimilates members of the Muricidce. 



Indeed, I know several conchologists who are of opinion 

 these two genera should be merged, and, as I have already 

 observed, it is only on account of the irregularity in size of 

 some of the lateral denticles, and especially in deference to 

 Mr. Cooke and Mr. Gwatkin's strongly expressed opinion, 

 that I have not done so at the present opportunity. 



(VII.) Iridescence of Epidermis in certain species. — In 

 three or four species the epidermis, when wetted or oiled, 

 shows prismatic reflections. I do not know this peculiarity 

 in any other genus, nor does it exist in many Latiri. It is 

 most conspicuous in the still uncommon L. prismaticus of 

 Martyn, who, under its old title, Bticcinuin prismaticuiny 

 figured it in his Univ. Conch., Vol. II., p. 2. This work, 

 begun in 1784, is more noteworthy on account of its 



