GASTEROPODA NUDIBRANCHIATA. 
41 
similar to those in Doris, are four, and sometimes six others, simply 
pointed* * * § . 
Tritonia, Cvv. 
Have the body, the superior tentacula and genital organs as in Doris ; 
but the anus and the orifice through which the peculiar liquid is ex- 
creted, are pierced on the right behind the organs of generation; 
the branchiae, which resemble little trees, are arranged along the sides 
of the back, and the mouth, provided with broad membranous lips, is 
armed inside with two horny and trenchant lateral jaws, which may 
be compared to a pair of sheep-shears. 
Trit. Hombergii, Cuv., Ann. du Mus,, I, xxxi, 1, 2, and the 
Journ. de Phys., 1785, October, pi. ii. A large species of a cop- 
per colour, from the coast of France. 
The same locality produces many others which vary greatly 
in size and the form of their branchiae f ; several of them arc 
very small j. 
Thethys§, Lin. 
Have all two rows of branchiae resembling branching tufts along the 
back, and a very large membranous and fringed veil on the head, 
which shortens as it curves under the mouth ; this latter is a membra- 
nous proboscis without jaws ; on the base of the veil are two com- 
pressed tentacula, from whose margin projects a small conical point. 
The orifices of the genital organs, of the anus, and of the peculiar 
fluid are situated as in the Tritonise. The stomach is membranous 
and the intestine very short, 
T. fimbria, L.,; Cuv., Ann. du Mus., XII. xxiv||. Grey 
spotted with Avhite ; a beautiful species from the Mediterranean. 
ScYLL,EA, Lin. 
Have the body compressed ; the foot narrow and marked with a fur- 
row which enables it to clasp the stems of the fuci ; no veil ; the 
* Doris quadrilineala, 'MuW., Zool., Dan., I,xvii , 4 — 6, and better, lb., cxxxviii, 
5 — 6; D. corniita, Ib., cxlv, 1, 2, 3; — D, flava, Lin. Trans., VII, A-ii. p. 84 ; — 
Puli/cera lineafa, Risso, Hist., Nat., IV, pi. i. f. 5. 
"t* Such are Trif. elegans, Descr., de I’Eg. Zool., Gaster.,pl. 2, f. 1 ; — Trit. rubra, 
Leuck., App., Rupp., Invert., pi. 4, f. 1 ; — Tr. glauca, Ib., f. 2 ; — T. cyanohranchiata, 
Ib., f. 3 ; — T. arborescens, Cuv., Ann. du Mus., VI, Ixi, and three others, at least 
closely allied ; — Doris arborescens, Streem., Act., liafn., X, v. 5 ; — Dons frondosa, 
Ascan., Act. Drouth., V, v, 2, and Doris cervina, Bommd, Act., Fless., 1, iii, 1. 
+ Doris coronafu, Bommd, Ib., and Doris pinnafijida, Lin. Trans., VII, vii, which 
is closely allied to it ; — Doris Jimbriafa, MiilL, Zool. Dan., CXXXVIII, 2, and pro- 
bably Doris clauigera. Mull., Ib., XVII, 1 — 3. Perhaps the Doris lacera, Zool. 
Dan., CXXXVIII, 3, 4, should also be referred to this genus. 
§ From St&uiar, a name employed by the ancients to designate the Ascidias ; Lin- 
naeus applied it to this genus. 
11 The difference observed beDveen the Thethys Jimbriafa, Bohatsch., Anim. Mar., 
pi. V, and the Thethys leporina. Fab., Column., Ag., pi. xxvi, appears to me to be the 
result of a greater or less degree of preservation. 
