OPISTHOBRANCHIATA PTEROPODA. 



53 



or mantle. The gills project freely on the dorsal suiface, and may 

 receive appendages of the alimentary canal. 



Fam. Tritoniadae. Gills in two longitudinal rows on the back. Tritonin. 

 Hmnbergii Cuv., Scyllcsa pelagica L. 



To this family is allied Tethysfimbriata L., with con- 

 centrated ganglionic mass, without radula and buccal 

 mass. 



Fam. Dorididae. Gills in circle round anus (fig. 523). 

 Doris coccinca Forb., JD. tuber culata Cuv., Adriatic and 

 Mediterranean, 



Fam. JEolididse. Numerous processes on dorsal surface, 

 into which diverticula of the alimentary canal pass 

 (PJilclenterata). JEolis paplllosa L. (fig. 525), Tergipes 

 ^dwardsi Nordm. Here are allied PhyllirJioe bucepha- 

 luin Per., and the Pliyllidiidce. 



Sub-order 3. Saccoglossa. Gills absent, or as 

 simple appendages of the dorsal integument. The 

 radula with a single row of toothed plates, of which 

 the anterior, after they are worn out, fall into a 

 pocket developed on the floor of the buccal cavity. 



Fam. Limapontiadse. Limapontia atra JohnsK 



Fam. Elysiadse. Elysia viridis Ok. Bal paping,. 



Class III PTEROPODA. * 



Hermaphrodite Mollusca without sharply separated head, with two 



wing-like fins, often 



with cephalic cones. 



The body is sometimes 

 elongated and straight, 

 sometimes with its hinder 

 part spirally rolled. The 

 anterior region bears the 



* Bang et Souleyet, "His- 

 toire nature! le des Mollusques 

 Pteropodes." Paris, 1852. 



C. Gegenbaur, " Unter- 

 suchungen iiber die Ptero- 

 poden und Heteropoden." 

 Leipzig, 1855. 



A. "Krohn, Beitrage zur 

 Entwickelungsgeschichte der 

 Pteropoden und Heteropo- 

 den." Leipzig, 1860. 

 H. Fol, " Sur le d^veloppement des Pteropodes." Archives do Yioolog'w 

 xperimentale, etc., Tom. IV., 1875. 



PIG. 52(3. a, Pneumodermon violaceum from the ventral 

 side, b, Clione auntralis from the side (Bronn). Ft, 

 fins ; Te, tentacles. 



