Lamarck's Genera of Shells. 229. 



South of Europe. PI. VII. Fig. 117. 19 recent species, and 

 1 fossil. 



4. Pileopsis*. 



Shell univalve, oblique-conical, curved forwards ; summit 

 bent, almost spiral ; aperture rounded oval ; anterior margin 

 shortest, acute, terminating in a slight sinus ; posterior margin 

 larger, round ; an elongated, arched, transverse muscular im- 

 pression under the posterior border. 



Animal. — Two conical tentacula, with eyes at their external 

 base. Branchias disposed in a row under the anterior border 

 of the cavity, near the neck. 



According to M. Defrance, it is probable that the animal of 

 this species never removes itself from the place where it has 

 once fixed. He observed, in some fossil species, a support 

 formed for the shell, during the life of the animal, by successive 

 depositions of testaceous matter, constituting a separate piece, 

 attached to marine substances, and preserving, on its upper 

 part, a pretty deep impression of the margin of the shell. 



Lamarck subdivides this genus into, 1, Shells without any 

 known support; and, 2, Shells with a supportt. The first 

 subdivision contains eight species, the second two. Only the 

 first four species of the first subdivision are recent shells, all 

 the rest are fossil. 



Type. Pileopsis ungarica %. (Patella ungarica. Linn.) 



• From TO-iXoc, a ftonnef, and o-J-i?, appearance, denoting the bonnet sL,ape 

 of the shell. 



t In the first number of his Genera of recent and fossil shells, Mr. G. B. 

 Sowerby gave his reasons for considering the Hipponix oi De France (Pi- 

 leopsis of the second subdivision, La»narc7c) to be a true bivalve shell, the 

 " support" being, in fact, the lower valve; and in the 15th number, just 

 published, he adds the following additional arguments in confirraatio;i of 

 his opinion: " Lamarck's Calyptraciais are Gusleropodes ; the shell being a 

 testaceous deposition from the mantle, and the Gasteropodes, not being 

 furnished with such a mantle under their foot, could not possibly deposit 

 testaceous matter in such a position, as to form what he has termed a 

 support, but which should more properly be called another valve ; conse- 

 quently, his ' Cabochons ayant un support connu' should be placed among 

 the Conchifera, or we must suppose the absurdity of a Gasteropoda depo- 

 siting shelly matter from the lower part of its foot, where it is not furnished 

 with the necessary organs."— This appears to us to be perfectly conclusive. 



t Hungarian. 



