182 LECTURES ON MOLLUSCA. 



times drive slioals of them on shore, where they are eaten for food. 

 They have a very large, irregular apex, surrounded by a keeled chan- 

 nel, and a twisted pillar. The Melos are brightly painted shells from 

 the East Indies, often with a pretty crown of spines around the short, 

 smooth spire. In Volutella (a tropical American shell) the expanded 

 mantle deposits a coat of enamel over the spire, which is often pro- 

 duced into a long horn. Voluta (proper) has a small operculum, and 

 numerous secondary plaits. The typical species, from the West In- 

 dies, is beautifully painted with a pattern resembling the staves of 

 music. The commoner species belong to the group Aulica, in which 

 the shell is generally tuberculated, with a sharp outer lip. In Sca- 

 phella, a southern form, also found fossil in the English Crag, the 

 shell is narrow and elongated. In Fidguraria, the shell is striated, 

 and the foot is comparatively small. In Callipara, the shell is like a 

 young cowry, with very small plaits. In Lyria, the shell is shaped 

 like Marginalia, with very small plaits, and ribbed exterior. It is the 

 only form of volute found on the west Coast* of America. 



The family of the Volutes make their first appearance in the creta- 

 ceous epoch, but very sparingly. In the tertiary groups, particu- 

 larly the Eocene of the London and Paris basins, a peculiar form 

 abounds, called Volulilites, in which the spire is sharp, as in Mitra, 

 and the plaits are often very faint. A single recent specimen of this 

 group was dredged in 132 fathoms of water, off the Cape of Good 

 Hope, during the voyage of the Samarang. 



Another group differ remarkably from the true Volutes in the shape 

 of the central teeth. Instead of having two large lobes on each side 

 of the small central one, they have only one central spike ; which rises 

 up so sharply from its arched support, that when arranged over each 

 other on the tooth-ribbon, they present the appearance of a keel. 

 There is no character in the shell by which the Amoria can be safely 

 separated from the ordinary Volutes. In the few specimens examined, 

 the surface is polished, and there are five oblique pillar-plaits. 



The same lingual detition is found in the little Volutomitra grarn- 

 landica ; remarkable as representing an essentially tropical type on a 

 boreal shore. The animal and shell are shaped for the most part as 

 in Mitra, from which the teeth are essentially different : so that it may 

 be either considered the representation of the Volutes among the 

 Mitres ; or, as placed by Dr. Gray, the mitred element among the 

 Volutes. 



Family Mab,ginellid2e. 



The Margindlas are a numerous group of very pretty little shells, 

 great favorites with collectors from their high polish, and beautiful 

 colors. They are almost all from the tropical seas, and the largest 

 number of finest species are from Africa. If we judge by the shells 

 alone, they form an exact transition from the Volutes to the Cowries ; 

 in their plaited pillar and general shape resembling the former, in 

 their glossy coat and thickened lip the latter family. Indeed the tran- 

 sition-genus Erato is placed by systematists sometimes in one, some- 

 times the other group. But so far as the animals are yet known, 



