BRITISH NUDIBRANCHIATE MOLLUSCA. v 



but, the anterior and posterior ones being bifid, there are twelve points, which without minute 

 inspection may be taken for distinct plumes. 



Idalia aspersa has been found at Bray, near Dublin, by Dr. Ball. 



(13) Idalia iNiEQUALis. 



Idalia incequalis, Forbes, Brit. Moll., v. 3, p. 579, pi. yy, fig. 4. 



" Body oblong, flattened, but very thick, truncate in front, suddenly tapering, pointed 

 behind. Back circumscribed, elevated, with steep sides. Dorsal tentacula linear, laminated ; 

 tentacular appendages set well apart, filiform, the anterior pair shortest, the lateral or posterior 

 pair very long, longer than the tentacula immediately in front of which they are set. The 

 animal when crawling usually carries its tentacles obliquely reflected, the anterior appendages 

 curved upwards, and the long ones directed sideways and backwards. The branchiae are 

 from seven to nine in number, forming a complete and erect circle ; on each side of them are 

 five or six rather short, unequal filamentous processes, the anterior ones approximated. The 

 general colour is grey, speckled with white, yellow, and brown. An opaque yellow line runs 

 down the centre of the tail, with dots of the same colour on each side of it. The sides of the 

 back are speckled with madder-brown and yellow. The branchial plumes are tipped with 

 purplish-brown, and banded centrally with white. The length of the body is rather more 

 than half an inch. 



"Two examples of this beautiful sea-slug, nearly allied to the last (I. aspersa), but 

 possessing distinct characters in the proportions and disposition of the tentacular and branchial 

 appendages, were dredged in thirty-five fathoms water on a sandy bottom in St. Magnus' Bay, 

 Zetland (M' Andrew and E. F.) When kept they appeared to be sluggish and very glutinous 

 to the touch." 



We have been favoured with an examination of these specimens in spirits. They come 

 very near to our I. aspersa ; the principal difference being in the disproportionate length of the 

 anterior filaments, and in the number of branchial plumes. These latter are nine, the anterior 

 one bifid. The posterior lateral filament on each side is also bifid. 



(14) Idalia pulchella. 



A single specimen of this little Idalia was obtained by Mr. Barlee, while dredging off 

 St. Ives, Cornwall, in the summer of 1853, and was sent to us in spirits. Its chief 

 characteristics are, the subclavate tentacles, laminated for three fourths of their length, the 

 expansion of the pallial margin in front, and the great size of the bifid posterior filaments. Its 

 colour is also somewhat different from that of the other species, being when alive, Mr. Barlee 

 informs us, delicately freckled with a very light lilac colour. It was got among corallines in 

 about twenty fathoms. 



(15) Idalia quadricornis. 



Doris quadricornis, Mont., in Linn. Trans., v. 11, p. 17, pi. 4, fig. 4. 



Mem., Brit. Anim., 283. 

 Idalia quadricornis, For. and Han., Brit. Moll., v. 3, p. 580. 



