DOLABRIFERA. 117 



or absent ; radula with a well-developed median series of teeth, larger 

 than the lateral teeth, and bilobed, spreading, at base. 



Four genera compose this subfamily, which is decidedly more 

 allied to the AplysiincK than to the Dolabellince. The anterior inser- 

 tions of the pleuropodia are contiguous, as in the latter group; but 

 the dentition, and the forward situation of the genital orifice agree 

 with Aplysiince. 



Genus III. DOLABRIFERA Gray, 1847. 



Dolabrifera GRAY, P. Z. S., 1847, p. 162 ; type Dolabella dolabri- 

 fera. Aplysia and Dolabella of some authors. ? ThallepusSwAixs., 

 Malacol., p. 250, 359. Dolabrifer FISCHER, Man. Conchyl., p. 568. 



General form ovate-oblong or sack-like, tapering toward the head. 

 Tentacles and rhinophores slit and expanded distally, the latter 

 nearer to the front margin than to the dorsal slit. Eyes as in 

 Tethys. Pleuropodial lobes arising far behind the middle of length, 

 contiguous, scarcely mobile, united behind, enclosing a large gill- 

 cavity ; dorsal slit short. Mantle small, not perforated over the 

 shell, nor covering much of the gill. Foot broad, often expanded 

 at the edges. Genital pore in front of the gill, under the mantle- 

 edge. 



Shell small, not spiral, solid and calcareous ; subtriangular, trape- 

 zoidal or irregularly oblong; the apex projecting and calloused, 

 with no spiral tendency. 



Radula with large, subtriangular rhachidian teeth, with several 

 denticles on the cusp ; lateral teeth with long, coarsely denticulate 

 cusps (see under D. ascifera). 



Type, D. dolabrifera Cuvier. 



Distribution, tropical shores in both hemispheres; one species 

 from Greenland. 



This genus is allied to Petalifera in external characters and the 

 solid, calcareous shell ; but it differs in having the mantle completely 

 closed over the shell, while in Petalifera there is a large orifice ex- 

 posing part of the shell. Dolabella resembles Dolabrifera in the 

 form of the body, short posterior branchial slit, etc., but it differs 

 radically in the dentition, the position of the female genital orifice, 

 and the spiral apex of the shell. 



A considerable number of species are known more or less per- 

 fectly from the Indo-Pacific area, with a few from tropical America. 



