102 Mr. Forbes on new British Mollusca. 



stellate figures coalesce — which they rarely do — so as to cover 

 the surface of the plant, the form and arrangement of the 

 cells, as just mentioned, are generally preserved. When de- 

 viations from this arrangement do occur, the general form of 

 the zoophyte is the most obvious character. This species 

 first occurred to me in Belfast Bay, in September, 1833, when 

 a quantity of tangle^ Laminaria digitata, had been thrown 

 ashore, on the broad leaves of which its stellate form at once 

 arrested my attention. In Strangford lough I similarly 

 found it afterwards; and more recently in Scotland, near 

 Ballantrae (Ayrshire), on Fucus serratus, but not in perfection 

 on this plant, whose leaves are too narrow to permit its per- 

 fect growth : on the shore at Leith too I have gathered it ; 

 and on a specimen of Nitophyllum Gmelini, from Sidmouth, 

 favoured me by Dr. Greville, it appears. Its distribution 

 would thus seem to be extensive. 



I lately ascertained that it had been found by Dr. Drum- 

 mond, many, perhaps thirty, years ago, at Larne. In the 

 Supplement to Dr. Johnston^s British Zoophytes the species 

 will be figured. 



To my accomplished friend Edward Forbes, Esq., I am 

 indebted for the figures which illustrate this paper ; without 

 the aid too of his superior knowledge, a portion only of the 

 species here introduced as new could, with any degree of 

 certainty, have been announced as such. 



REFERENCES TO PLATE II. 



Fig. 1. Doris sublsevis. 



2. lanthina nitens ? 



3. Tritonia lactea, 



4. Euplocamus plumosus. 



5. Poly cera ty pica. 



6. Poiycera quadrilineata, var. 



Fig. 7. Goniodoris elongata. 



8. Cerithium reticulatura, var, 



9. Rissoa Ballias. 



10. Rissoa tristriata. 



11. Rissoa Harvey i. 



XII. — On some New and Rare British Mollusca. By Ed- 

 ward Forbes, M.W.S., For. Sec. B.S., &c. 



[With a Plate.] 



I. Doris Argo. Dr. Johnston pointed out some time ago 

 that the Doris Argo of Pennant and British authors generally 



