340 MOLLUSCA. 



Onchidora, Blainv. 



Only differs from Doris in the separation of the genital organs, the 

 orifice of which communicates by a furrow running along the right 

 side as in Onchidium(l). In the 



Plocamoceros, Leuck. 



We find all the characters of the Onchidorae, in addition to which 

 the anterior margin of their mantle is ornamented with numerous 

 branched tentacula(2). 



POLYCERA, CuV. 



The branchiae, as in Doris, on the hind part of the body, but more 

 simple, and followed by two membranous laminse, which cover them 

 in moments of danger; anterior to the claviform tentacula, similar 

 to those in Doris, are four, and sometimes six others, simply point- 

 ed(3). 



Tritoxia, Cuv. 



The body, superior tentacula and genital organs as in Dorisj but the 

 anus and the orifice through which the peculiar liquid is excreted, 

 are 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 in- 

 side with two horny and trenchant lateral jaws, which may be com- 

 pared to a pair of sheep-shears. 



Tnt. Hombergii^ Cuv., Ann. du Mus., I, xxxi, 1, 2, and the 



lb., Id, 3; — D. solea,Id., lb., 1, 2; — D. scabra, Id., lb., p. 446; — D. maculosa, Id., 

 lb.; — D. tomentosa. Id., lb.; — D. nodosa, Montag"., Lin. Trans., IX, vii, 2; — D. 

 marginata, Lin., Trans., VII, vii, p. 84; — D. nigricans. Otto., Nov. Act. Nat. 

 Cur., XIII, part II, pi. xxvi, f. \,—D. grandijlora. Id., lb., XXVII, f. 3,—D. 

 iigrina, Sav. E^yp., Gasterop., pi. i, p. 3; — D. concentrisca, lb., f. 5; — D. marrno- 

 rata, lb., f. 6, &c. 



Prismatic species, where the mantle is almost as narrow as the foot : Doris 

 lacera,C\iv., Ann. du Mus., IV, Ixxiii, f. 1 and 2; — D. atromarginata. Id., lb., 

 Ixxlv, 6; — D. pustulosa. Id., lb., p. 473; — D. gracilis, Rapp., Nov. Act. Nat. 

 Cur. Xni, part 11, pi. xxvii, f. 10. See also Van Hassel. Bullet. Univ., 1824, 

 Octob., Zool., p. 235. 



(1) Onchidura Leachii, Bluinv., Malac, pi. xlvi, f. 8. 



(2) Plocamoceros ocellatus, Leuck., App. Ruppel., Invert., pi. 5, f. 3. 



(3) Doris quadrilineata, Miill., Zool., Dan., I, xvii, 4 — 6, and better, lb., 

 cxxxviii, 5 — 6; — D. cornuta, lb., cxlv, 1, 2, 3; — D. flava, Lin. Trans , VII, vii, p. 

 84; — Polycera lineaia, Risso, Hist., Nat,, IV, pi. i, f. 5. 



