I50 Transactions of the Royal Canadian Institute 



BRANCHIATA themselves are split into two tribes, the Holohepatica and 

 the Cladohepatica. This classification as its terminology im.plies is 

 based in the main upon the condition of the liver, i.e., as to whether or 

 not it is split up, but this accompanied also, by other anatomical features. 



Description of the Species. 



Tribe I. Holohepatica. 



Nudibranchs in which the liver forms a compact mass, neither 

 branched nor divided. Usually accompanied by the following characters. 

 Almost complete external symmetry ; vent usually on the mid dorsal line 

 and surrounded by a circle of branchial plumes ; radula of moderate or 

 considerable width and not known to be reduced in any genus ; mandibles 

 are rare; hermaphrodite gland not a separate mass but spread over the 

 liver as a layer; as a rule the genital ducts are triaulic and there are two 

 receptacula seminis. 



Family Tritoniidae. 



Branchiae consisting of tufts set along the mantle margin or occa- 

 sionally altogether absent. 



Genus Tritonia (Cuv). 



Alder and Hancock, Mon. Brit. Nud. Moll., Pt. VH, 1855. p. 46. Proc. 



Ac. Nat. Sci. Philadelphia, Pt. I, 1879. p. 95. Bergh, Malacol. 



Untersuch, Vol. HI, Heft 15, 1884. Bull. Mus. Comp. Zool., 



Harvard, Vol. XXV, No. 10, 1894. p. 146. Eliot. Brit. Nud. Moll., 



Pt. VHI, 1910. p. 145. 

 "The body is limaciform but somewhat rectangular in outline, except 

 at the end where it tapers to a short tail. The foot is broad. Over the 

 mouth is an oral veil bearing two grooved tentacles at the end, and in 

 the middle tubercles or processes. The rhinophores are retractile into 

 raised sheaths; not perfoliate but surrounded by a few plumes. The 

 dorsal margin is slightly prominent and bears a single row of branchial 

 tufts which are more or less arborescent. Anal and rectal openings on 

 the right side. Jaws large with several rows of denticles or prominences 

 near the edge. The radula varies greatly in size in the different species, 

 but always consists of a broadish central tooth with a moderate or large 

 number of laterals which are usually simply hamate. The first lateral 

 is usually larger and lower than the others and somewhat clumsily 

 shaped. The liver is not divided and sends off no branches to the gills. 



