FAMILY DORIDjE DORIS. "3^ 



ORDER III. GASTEROPODA. 



Body free, without any distinct arms, hut with a fleshy foot extending under the body, 

 adapted for crawling, and. in a few cases for swimming. A distinct head, furnished with 

 one or several pairs of tentacula. Upon or near these are placed the eyes. Shell either 

 entirely ivanting or rudi7nentary , hut for the most part complete. Generative organs 

 usually on the right side. 



Obs. This order embraces an immense number of Mollusca, particularly of those furnished 

 with shells, which are usually termed shellfish. Their number requires their division into 

 several orders, or, as we shall term them, sections, divided after Cuvier from the form and 

 position of the gills or lungs. 



SECTION 1. NUDIBRANCHIA. 



Gills in naked tufts rising from the hack, always symmetrical either on the sides or median 

 line. No shell ivhatsoever. Marine. 



Obs. We have numerous species on our coast, but they have not yet been much studied. 

 They are often seen swimming in a reversed position, employing the margin of their mantle 

 and the tentacula as oars. Others are found in the ocean, attached to fuci. 



FAMILY DORID^. 



With four tentacula ; two above, and two beneath under the edge of the mantle. Gills 

 arborescent, and forming on the median line a group around the vent. 



GENUS DORIS. 



Body oblong, flattened or cylindrical, bordered with a loose membrane surrounding it, and 

 extending occasionally beyond the head. Upper tentacula on the anterior part of the body, 

 in a cavity ; the other two, conic, and situated under the anterior edge of the mantle. Mouth 

 at the extremity of a small tube. Foot oblong. Vent on the median line, on the posterior 

 part of the back. Gills prominent, fringed and laciniated. Sexual orifice under the righi 

 margin of the mantle. 



