OPISTHOBRANCIIIATA PTEROPODA. 



53 



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

 receive appendages of the alimentary canal. 



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

 Hombcrijii <_'uv., SeyllcBO, pelagica L. 



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

 centrated ganglionic mass, without radula and buccal 

 mass. 



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

 Doris coccinca Forb., D. tuberculata Cuv., Adriatic and 

 Mediterranean. 



Fam. .ZEolididae. Numerous processes on dorsal siirface, 

 into which diverticula of the alimentary canal pass 

 (Phlebenterata). JEnli*iHip'illom.\^. (fig. 525), TcrgijH-x 

 Eihcardsi Nordm. Here are allied Phyllirlioe luccplia- 

 Itim Per., and the PliyUiiliidfe. 



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. 



FIG. 525. ^EoZ?8 pnptt- 

 Fam. Limapontiadae. Lnnapontia atra Johnst. J s (Bronn). Rp, dor- 



Fam. Elysiadae. Elysia mridis Ok. sa l papilla. 



Class III. PTEROPODA. * 



Hermaphrodite Mollusca without sharply separated head, with two 



large wing-like fins, often 

 ivith 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 naturelle des Mollusques 

 Pteropodes." Paris, 1852. 



C. Gegenbaur, " Unter- 

 suchungen iiber die Ptero- 

 poden und Heteropoden." 

 Leipzig, 1855. 



A. ' Krohn, Beitrage zur 

 Entwickelungsgeschichte der 

 1'teropoden und Heteropo- 

 den."i Leipzig, 1860. 



H. Fol, " Sur le deVeloppement des Pteropodes." Archives da 

 experimentale, etc., Tom. IV., 1875. 



FIG. 523. 7, Pneiimodermon violaceum from the ventral 

 side. I, Cllone australls frqm the side (Bronn). Fl, 

 fins ; Tt, tentacles. 



