MARSHALL: ADDITIONS TO 'BRITISH CONCHOLOGY.' 245 



on the hinge-line, and pouting on the ventral side, with 

 the valves more convex. Dredged off Guernsey in i8 — 20 

 fathoms. This variety somewhat approaches a Litho- 

 doimis in shape. 



M. barbatus var. depressa Marsh. Shell narrower at the 

 anterior and broader at the posterior end, corresponding 

 with the var. ovata of M. modiolus, and found in similar 

 situations, wedged in the crevices of rocks between tide- 

 marks. Herm Island (J. T. M.) ; Gouliot Caves, Sark 

 (Jeffreys) ; Jersey, rock-pools and crevices of rocks (Du- 

 prey). It derives its peculiar shape from becoming in an 

 early stage of growth wedged in the crevices of rocks, 

 which contract the umbones and prevent development in 

 that part, while giving free play for expansion at the 

 opposite end. 



Nucula nitida var. radiata Marsh. Shell having coloured 

 rays. Found with the type. 



N. nitida var. turgida Marsh. Shell more triangular, and 

 umbones more swollen. ' Annals,' December, 1875. Dr. 

 Jeffreys described in the 'Annals' for 1879 a var. ve/ifrosa, 

 'swollen and smooth,' from the Mediterranean, which I 

 take to be the same thing. 



Pectunculus glycymeris var. pilosa L. Mentioned in 

 ' B. C. ' by Jeffreys, but not formally described. 



P. glycymeris var. decussata Turt. Mentioned in ' B. C 

 by Jeffreys, but not formally described. 



P. glycymeris var. nummaria Turt. Mentioned in 'B. C 

 by Jeffreys, but not formally described. 



Area obliqua Phil. This species does not appear in Somer- 

 ville's List ; but as Jeffreys described and figured it upon 

 what he thought sufficient grounds, it would be well to let 

 it keep its place in the British List tentatively. 



Area nodulosa Miill. Mr. Frank Coulson, of Glasgow, 

 dredged a living specimen off East Shetlands in 1886. 



