FAMILY DORIDZ — DORIS. ia 
ORDER III. GASTEROPODA. 
Body free, without any distinct arms, but 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 wanting or rudimentary, but for the most part complete. Generative organs 
usually on the right side. 
Oss. 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 back, always symmetrical either on the sides or median 
line. No shell whatsoever. Marine. 
Oss. 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, 
ina 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 right 
margin of the mantle. 
