218 ARCADiE. 



curling around the anterior muscle, of a pale brown 

 colour." The vibratile cilia of the branchiae are very large. 

 It is distributed, often in great abundance, all around 

 our shores. It frequents a coarse bottom and rather deeper 

 water — from seven to ten fathoms — than its near ally 

 nitida (S. H.). It occurs also, and in sufficient plenty, 

 usually on a bottom of gravel or muddy gravel, at much 

 greater depths, as twenty, thirty, forty, and even as deep 

 as eighty and ninety fathoms (E.F.). It ranges through- 

 out the European seas, and occurs fossil in both red and 

 coralline crags.* 



N. NITIDA, Sowerby. 



Triangular, either rayless, or with the rays linear and dark 

 grey ; epidermis highly lustrous ; hinder extremity tapering, its 

 dorsal area not sculptured ; inner margin crenated. 



Plate XLVII. fig. 9. 



Area nucleus, Mont. Test. Brit. p. 14 (chiefly). — Dillw. Recent Shells, vol. i. 



p. 244 (in part). 

 Nucula nitida, Sowerby, Concholog. Illustrations, Niicula, No. 29, f. 31. — 



Hanley, Recent Shells, vol. i. p. 171, pi. 19, f. 44. 



So closely does this shell approach the preceding in 

 general features, that in place of recapitulating character- 

 istics common to both, we shall merely indicate their 

 points of difference. That most immediately perceptible is 

 the highly lustrous epidermis of an ashy olive colour, 

 beneath which the surface is occasionally adorned with 



* The A': argentea of Brown (Illust. Conch. G. B. p. 85, pi. 33, f. 14, 15.) 

 solely constituted from a single valve of little more than a line in length, and said 

 to resemble the fry of N. margaritacea, is thus described : — 



" Obliquely ovate, very glossy, and smooth ; colour olivaceous ; umhones 

 placed much to the posterior side, with a cordiform depression beneath ; inside 

 glossy, silvery white; hinge with 1 2 (!) rather strong, regular, upright teeth ; 

 margins with very fine crenulations. — Dunbar." 



