134 VITRINIDJE. 



Genus YITRINOPSIS, Semper, 1873. 



Shell resembling Yitrina, protected by two mantle-lobes, one 

 of which is on the right side and anterior, the other on the left 

 side. No mucous pore. Marginal teeth tricuspidate. 



Philippines. 



Genus PARMELLA, H. Adams, 1867. 



Known only by its shell. Depressed, spire flat, epidermis 

 horny, polished, extending greatly beyond the posterior part of 

 the margin. 1 sp. Fiji Islands. 



Possibly identical with Yitrinopsis. 



Genus YITRINOCONUS, Semper, 1873. 



Shell thin, umbilicated, helicoid, spire conical, with obtuse 

 apex ; whorls planulate, the periphery of the body-whorl more 

 or less angulated, and the base flattened ; aperture lunate, with 

 sharp or thickened petistome, cervical lobes of the mantle mod- 

 erate, no polishing lobe as in Yitrina; locomotive disk longi- 

 tudinally tripartite. Marginal teeth bicuspidate (PK 29, fig. 5). 



Philippines. 



Differs from Zonites in the absence of the mucous pore and in 

 having the tripartite locomotive disk. 



Genus PLUTONIA, Stabile, 1864. 



Body compressed and carinated behind, rugose; mantle 

 median, free in front, with posterior pulmonary orifice; posterior 

 extremity subtruncated, without mucous pore; jaw without ribs 

 or median rostriform protection ; teeth like Testacella. Internal 

 shell-plate oblong, Ancyliform, with a rudimentary spire. Azores. 



The shell of this genus was considered by Morelet and Drouet, 

 who described it, a recent representative of the genus Yiques- 

 nelia, Desh., 1857 ; a name given to certain nummulitic fossils of 

 Roumelia. The identification was, however, imaginary. 



This and the following genus, together with Selenites (Helix 

 concava, Say), constitute the family Selenitidse, Fischer, char- 

 acterized by the dentition of Testacellida3, with the jaw of Linia- 

 cidae (Jaw, PI. 29, fig. 6; dentition, PL 29, figs. 7-9> 



