302 THE DOLABELLINAE. 



Visceral commissure usually very much shortened, except in Tethys and Dola- 

 bella. Genital duct monaulic, the hermaphroditic duct connected with the 

 penis by a ciUated groove. 



Aplysiidae. 



Animal lengthened, not protected by a shell, the neck and head narrower 

 than the body; mouth a vertical fissure; anterior angles of the head produced 

 into two tentacular lobes folded above; behind them the cylindrical or conical 

 rhinophores, sUt above, in front of which are the minute eyes. Parapodia 

 recurved over the back, forining two lateral or dorsal lobes enclosing the mantle 

 and ctenidium. Genital orifice between the dorsal lobes, communicating by 

 a long furrow with the evertible penis, which is near the anterior right tentacle. 

 Shell nearly or entirely covered by the mantle, uncoiled, in the form of a con- 

 cave plate, or absent. Mouth with corneous jaws and a large multiserial radula 

 composed of similar teeth; stomach armed with horny nodules; anus behind 

 the branchial plume. 



Aplysiinae. 



Parapodial lobes well developed, their anterior ends separated; genital 

 orifice in front of the ctenidium; radula with mde denticulate rhachidian 

 teeth, and narrower serrate and denticulate laterals. Shell flexible. 



DOLABRIFERINAE. 



Parapodia considerably united beliind, in front contiguous, separated only 

 by the spermatic furrow; genital orifice in front of the ctenidium; shell calca- 

 reous or absent; radula with well-developed rhachidian teeth, larger than the 

 laterals. 



DOLABELLINAE. 



Parapodia scarcely mobile, united behind, inclosing a large branchial 

 chamber, their anterior ends contiguous, separated by the spermatic furrow; 

 the dorsal slit short. Posterior part of body obliquely truncate, bounded by a 

 ridge; Genital orifice usually under the posterior part of the ctenidium; radula 

 with the rhachidian tooth rudimentary or nearly so, laterals very numerous 

 with long simple cusps; shell well developed, calcareous. 



