Fam. 3, Plate 10. 



Figs. 5 and 6. 

 EOLIS ALDERI, Cocks. 



E. griseo-albida, depressa; branchiis subconicis, leviter depressis, seriebns 12 — 14 crebre digestis, 

 ordinibus 2 vel 3 anterioribus albis, reliquis griseo-fuscis, apicibus flavis ; tentaculis flavis ; angulis 

 anterioribus pedis paululum prodnctis. 



Eolis Alderi, Cocks, in Naturalist, v. 2, p. 1, pi. 1, f. 1. 



Hab. In pools between tide-marks, Gwyllyn Vase, Falmouth, W. P. Cocks, Esq. 



Body five to seven tenths of an inch in length, transparent white, with opaque white 

 spots. Dorsal tentacles linear, nearly smooth or a little wrinkled, approximating, of moderate 

 length and bright yellow. Oral tentacles a little longer than the dorsal ones, white tipped 

 with yellow, set rather above the margin of the head. BrancJiice very numerous, sub-conical, 

 a little flattened, and tapering gradually towards the top ; arranged in from twelve to fourteen 

 dense rows, nearly covering the whole of the back, extending round the sides of the head in 

 front, and reaching very nearly to the tail behind. The first two, or sometimes three, rows are 

 opaque white, the remainder are gray marbled with pale purplish brown, and profusely spotted 

 with white : the apices are yellow or pale orange with the extreme tips pale. Foot transparent 

 white, a little rounded in front, and produced into short angles at the sides ; the posterior 

 extremity is extended into a fine point. 



For the knowledge of this species we are indebted to our friend Mr. W. P. Cocks, who 

 found it very abundant at Falmouth in the summer of 1848. During that year, he informs us 

 that he got nearly seventy specimens. It was scarce in 1849, and from that time to the 

 present he has not seen a single specimen. It comes very near to our E. glauca, but Mr. 

 Cocks, who has had the opportunity of studying both species in a living state, considers it quite 

 distinct. The white ruff, formed by the first two rows of papillae, he assures us is a permanent 

 and good character in this species, besides that it is never more than half the size of F. glauca 

 in the adult state, and the colour is also different. Unlike F. glauca, this is a very active and 

 restless creature, erecting its branchiae and shewing much irritability when disturbed. It 

 spawned profusely in confinement. The ova, which are deposited in July and August, are con- 

 tained in a pellucid membrane of a cylindrical form, attached by the lower surface. From the 

 drawings we have been favored with, it appears to form a much waved spiral, with a single row 

 of eggs sparingly distributed through it. In this character the spawn differs from that of any 

 other British Eolis. Mr. Gosse has observed a similar arrangement of the ova 'in Antiopa cristata. 



The specimen of this Eolis from which our drawing was taken is the only one that reached 

 us in a living state. 



Eig. 5. Eolis Alderi, side view. 



6. Two of the branchial papilla?, much enlarged. 



