Fam. 3, Plate 21. 



EOLIS ALBA, Alder and Hancock. 



E. gracilis, alba ; branchiis oblongis, sub-linearibus, albis, apicibus interdum fusco-cinctis, in fasci- 

 culis 5-6 digestis; tentaculis dorsalibus fuscis, superne in bnlbo expansis; angulis anterioribus pedis valde 

 dilatis. 



Eolis alba, Aid. and Hanc. in Ann. Nat. Hist. v. 13, p. 164. 



Hab. On sponge from shallow water, Malahide, near Dublin. Under stones at low-water mark, 

 Rothesay Bay. 



Body half an inch long, very slender, and tapering to a fine point behind ; pellucid white 

 with a yellowish tinge from the viscera shining through. A broad patch of opake white runs 

 along the head to the dorsal tentacles, passes in a narrow band between them, and is divided 

 behind into two branches extending to the first branchial papillae, where they again unite, 

 forming a triangle or lozenge-shaped patch, which is continued backwards, and assumes an 

 elliptical form over the heart ; it then contracts and passes in a single interrupted line down 

 the back to the tail. Dorsal tentacles rather long, smooth, approximating at the base, 

 tapering slightly for about three fourths of their height, when they swell into a bulb or button- 

 like expansion, above which they become more slender and taper to an abrupt point. They 

 are of a dark olive brown approaching to black below the bulb, and white above it. Oral 

 tentacles long, nearly linear, swelling a little at the base, and tapering at the point, which is 

 opake white, the rest transparent. They arise from the sides of the head, the form of which 

 they determine. They are usually held in a gracefully curved position. Head rather 

 narrow. Brancliice arranged in five or six clusters on each side of the back, four of 

 which are very distinct and well defined, the opposite ones approaching each other in the 

 centre more nearly than usual, and having a ruff-like appearance. The first and second 

 clumps which are at a considerable distance from each other, are composed of two transverse 

 rows each, six or seven papillae in each row ; the others are in single series, and decrease 

 towards the tail. The papillae are of moderate length, linear oblong, and slightly flattened 

 at the base, where they are pellucid and tinged with yellow from the central vessel appearing 

 through ; the rest is of an opaque white, excepting, in some specimens, a dark olive coloured 

 circle near their termination, above which is another band of opake white ; the apices are 

 pellucid. Foot narrow, nearly linear, and perfectly transparent, terminating behind in a very 

 fine point, extending considerably beyond the branchiae. The anterior angles are produced 

 into long, slender, tentacular processes, curved backwards. A deep groove extends across 

 the front of the foot to their points ; the central portion is curved inwards, giving the whole 

 of this part a bow-like outline. The eyes are conspicuous and placed as usual behind the 

 dorsal tentacles. 



