SCROBICULARIA. 437 



very short delicate and scattered minute nocculent marks, ap- 

 parently caused by an exfoliation of the epidermis : the ventral 

 margin is more evenly curved ; and the upper or dorsal margin 

 on the posterior side has the same curve and angle of inci- 

 dence as the lower posterior margin, both meeting halfway in 

 a rounded and upturned point ; the angle on this side is very 

 indistinct ; there is scarcely any depression below the beak on 

 the posterior side, the dorsal margin being more expanded : 

 the cartilage is golden-yellow and longer than in the other 

 species, and the pit is larger and more twisted : the inside is 

 lineated lengthwise, but is also microscopically fretted like 

 shagreen : muscular scars conspicuous, the anterior being ob- 

 liquely elliptical and the posterior triangularly eval. L. 0-45. 

 B. 0-8. 



Var. ovata. Shell more oval, often eroded near the beaks. 



Habitat : More local than S. prismatica, in muddy 

 sand, at from 3 to nearly 100 fathoms : south coast of 

 Cornwall (M 'Andrew); Dogger bank (Howse andMen- 

 nell) ; all the coasts of Ireland; west of Scotland; and 

 north and east of Shetland. The variety was taken by 

 Barlee and myself while dredging together in Birterbuy 

 Bay, co. Galway. Every writer on the Scandinavian 

 mollusca has noticed its occurrence in those seas, at 

 depths varying from 6 to 110 fathoms. The only south- 

 ern locality recorded is Algeria, on the authority of 

 M. WeinkaufF. 



The animal is quite as lively as its congener ; but the 

 shell gapes (or, for the sake of the antithesis, I may say, 

 yawns) much more. 



It is the Amphidesma intermedia of Thompson. If 

 the recognition of the Mya nitida of Muller depended 

 on the very obscure diagnosis in his f Prodromus/ I 

 should have felt the same disinclination as the authors 

 of the f British Mollusca ' to accept the last-mentioned 

 specific name ; but an article by Fabricius, in the fourth 

 volume of the ' Skrivter af Naturhistorie-Selskabet/ 



