1 90 MALACOZ9A. GASTEROPODA. NUDIBRANCIIIATi*,, 



2. Tritonia plebeia. Plebeian Tritonia. 



Body oblong, tapering to an obtuse point, convex above, 

 laterally compressed, flat beneath ; the mantle slightly rugoso- 

 granulate, not forming a margin laterally, but prolonged an- 

 teriorly into a kind of veil having seven prominent papilla?, of 

 which the lateral are longest ; tentacula cylindrical, obtuse, 

 divided into several pinnatifid segments, their sheaths with the 

 margin entire ; branchial tufts small, six on each side ; foot 

 oblong, without prominent margin ; upper parts greyish- 

 yellow, sides yellowish, variegated with tortuous branched 

 dusky lines, lower parts pale yellow. Length eight-twelfths 

 of an inch, height two-and-a-half twelfths. 



An individual from deep water off Aberdeen found by my 

 son John in March, 1842. 



Tritonia plebeia. Johnst. Edinb. New Phil. J ©urn. v. 77 ; Ami. 

 of Nat. Hist. i. 1 15. PI. 3. f. 3, 4. 



SECTION II.— CYCLOBRANCHIATA. 



Branchice in the form of arbuscules symmetrically disposed 

 around, or anteriorly to the anus ; ichich is placed in the 

 median line, near the posterior part of the body above ; the 

 skin tubercidated* 



Family I. — Dorina. 



Animal with the body oval or elliptical, flat beneath, 

 more or less convex above ; the head indistinct ; the 

 tentacula four, two larger on the head above, two smaller 

 near the mouth, nnder the edge of the mantle ; mouth 

 with a denticulate lingual mass ; the mantle covering the 

 body above, and projecting all round, so as to extend 

 beyond and conceal the head and foot, when the animal 

 is viewed from above ; the foot large, oval, elliptical, or 

 oblong ; the branchiae tufted, and disposed in a circular 

 form at the hind part of the body above, before the anal 

 aperture. 



The species, which are all marine, have a great resem- 

 blance to Slugs, and crawl much in the same manner. 



