284 MOLLUSCA. BRANCHIFERA. Tritonia. 



Length about a quarter of an inch, of a slender form, the front obtuse, ta- 

 pering behind, of a pale yellow, with minute pink spots ; tentacula slender, 

 filiform, with a large trumpet-shaped basilar sheath. 



Gen. XXXVIII. TRITONIA. — Branchial plumes in a 

 row on each side the back, and destitute of basilar sheaths. 



141. T. Hombergii. — Branchiae forming a continuous plu- 

 mose crest on each side the cloak, between which and the mar- 

 gin of the foot, the body is compressed and smooth. 



Cuv. Ann. Mus. i. t. xxxi. f. 1, 2 — (Limace de mer palmifere, Diquemare, 

 Journ. Phys. Oct. 1785, t. ii.)- Firth of Forth. 



Length upwards of 2 inches, sometimes approaching to 8 ; of a purplish 

 colour. Cloak convex, thickly covered with unequal soft tubercles ; tenta- 

 cula consisting of five plumose divisions, each surrounded at the base by a 



prominent ring This, the largest species of the genus, was first detected in 



our seas by J. G. Daly el, Esq. the learned author of the treatise on the 

 PlanaricB. 



142. T. arbor escens. — Branchiae, 5 or 6 on each side, in the 

 form of plumose tubercles. 



Doris arb. Mull. Zool. Dan. Prod. p. 229 — Fab. Fauna gr. 346. T. arb. 

 Cuv. Ann. Mus. vi. t. lxi. f. 8-10. Flem. Edin. Encyc. xiv. 619. 

 Length about an inch ; foot narrow, sides compressed ; cloak smooth, its 

 margin above the mouth with four plumose appendages ; branchiae decreas- 

 ing in size towards the tail ; tentacula conical, transversely striated ; the 

 sheath with a divided margin. I have found this species in the Zetland 

 Isles, agreeing with the characters of Cuvier, with this difference, that the 

 branchiae in his are only 5 on each side, while in our specimen they appeared 

 to be 6. But as the two posterior ones are very small, and as his examples 

 were preserved in spirits, it is probable that they have escaped detection. It 

 has likewise been found in the Frith of Forth, by Dr Grant, who, when keep- 

 ing it confined in a glass vessel, observed that it possessed the power of emit- 

 ing distinctly audible sounds. 



143. T. pinnatifida. — Branchiae 9 on each side, ovate and 

 imbricated with conical papillae. 



Doris pin. Mont. Linn. Trans, vii. 79. t. vii. f. 2, 3 — Coast of Devon. 

 Length T s 5 ths of an inch; body slender, rounded in front, tapering behind, 

 of a grey colour, spotted with green. Tentacula filiform, with a trumpet- 

 shaped basilar sheath. The branchiae are longer than the breadth of the 

 the body, and the papillae, which have black tips, are arranged in 5 or 6 

 whorls. 



144. T. bifida. — Branchiae, in a single row on each side, nu- 

 merous, unequal, ovate, pedunculated. 



Doris bif. Mont. Linn. Trans, xi. 198. t. xiv. f. 3 — Coast of Devon. 

 Length about a quarter of an inch ; body linear, acuminated behind, the 

 front rounded, of a whitish colour, with a reddish brown line on each side of 

 the back. Sheath of the tentacula broad, erect, bifid ; behind which are two 

 black eyes. Branchiae, 12 on each side, 3 in each division larger than the 

 rest, the club semitransparent, uniform on the surface, but complicated 

 within. 



