338 Mr. Alder on the Genus Polycera. 



identical with the Doris flava of Montagu,) which have been 

 described in a preceding Number of this Journal*. Of the three 

 species which I have met with on our coast, one is probably 

 the same with D. quadrilineata, Mull., and D. flava, Mont.; 

 the varieties I have met with inducing me to bring these two 

 together. A detailed description may enable others to judge 

 whether or not I am right in this view of the subject. 



Mollusca Nudibranchia, Cuvier. 



Fam. DORID^E, Johnston. 



Gen. Polycera, Cuv. 



a. With two branchial appendages, body without spicules. 



P. quadrilineata, Plate IX. fig. 1. to 6. 



Doris quadrilineata, Mull. Zool. Dan. t. 17 1; Prod. 2771. 

 Doris flava, Mont. Linn. Trans, vii. 79. t. 7. f. 6. 



P. White, with 5 rows of orange tubercles, 4 to 6 tentacular fila- 

 ments, 7 to 9 branchial plumes, and 2 branchial appendages. 



Variety, marbled with dark brown and orange, with 4 dark lines 

 along the sides, uniting the orange tubercles. 



Body nearly half an inch long, limaciform, prismatic, tapering to 

 a point behind, smooth, white, semi-transparent ; with two mode- 

 rately sized clavate and strongly lamellated tentacula, mucronated at 

 top, tipped with orange, non-retractile ; at a little distance behind 

 which are two very small black eyes. The anterior portion of the 

 body is produced into a kind of veil, the margin of which is adorned 

 with four, or sometimes six, linear tentacular filaments tipped with 

 bright orange. The sides of the mouth are produced into two angular 

 points, but not tentacular. Seven, or rarely nine, plumose branchiae 

 are situated about two- thirds along the centre of the back. They 

 are white tipped with orange ; the three anterior ones largest, the 

 others very small, surrounding the vent in an incomplete circle. At 

 the sides of these, and slightly posterior, are two plain, linear, 

 branchial lobes, about three times the length of the longest plumes, 

 abruptly tapering to an obtuse point, tipped with orange. Two 

 rows of orange or golden yellow tubercles, extending from the mar- 

 gin of the veil, form an elevated ridge on each side of the back to 

 the branchial lobes, beyond which they unite and form a central 

 carina to the tail. Another row of orange tubercles, not always 

 regular, occupies the centre of the back, and two others adorn the 

 sides between those first mentioned and the foot. Foot linear, very 

 narrow, truncated in front, where it forms two sharp angles, and 

 ending in a point behind. There is a strong groove down the centre, 

 and the margins can be brought together like the leaves of a book. 

 No cloak. The skin smooth and without any spiculce. Aperture of 

 the sexual organs on the right side, as in Eolidia. 



* Annals, vol. v. p. 92. 



t For the quotation from Muller I am indebted to my friend Mr. E. 

 Forbes. 



