SCROBICULARIA. 325 



Irish locality from which he has seen unquestionable spe- 

 cimens. 



The Sytidosmya truncata of Recluz (Revue Zoologique, 1843, p. 368 ; in 

 Chenu, Illust. Conch. Syndos. p. 4,) is entirely constructed from the Amphides- 

 ma truiicatum of Brown's Illustrations of the Conchology of Great Britain, p. lOG, 

 pi. 42, f. 4, a species which is rendered peculiarly obscure, through the drawing 

 and description being at variance, an error which, unfortunately, the author's 

 memory is unable to account for. Neither of them, however, suggests to us the 

 idea of its belonging to this genus, the figure, especially as regards the hinge, not 

 being unlike the young of our solitary species of Scrohicuhiria. Tlie reference to 

 the species so named in Fleming's work on the British Animals, would have led 

 us to the supposition that it was a Thracia, that shell being avowedly the Ana- 

 tina trimcata of Turton, which we know from the types to be a variety of Thracia 

 distorta, but the indicated teeth of the following description are entirely adverse to 

 such a conclusion, 



" Subovate, rather convex, oblique, anterior side produced ; posterior side 

 rather straight and subtruncated below ; with a flexure emanating from the 

 umbo, and terminating on the margin ; umbones small, nearly central and 

 slightly inflected, beneath them a lanceolate cavity or lunule, covered with trans- 

 verse nearly obsolete striae and wrinkles ; surface white, smooth, and glossy ; 

 hinge with a double primary tooth in each valve, and a small tooth-like knob in 

 the left valve, locking into a cavity for its reception in the opposite one ; inside 

 smooth, glossy, and white ; each valve provided with two large muscular im- 

 pressions ; margins rather thick for the size of the shell. Length three-eighths 

 of an inch ; breadth half an inch. Found at Greenock by Stewart Ker, Esq. 

 and is in the cabinet of Lady Jardine. 



SCROBICULARIA, Schumacher. 



Shell compressed, subequivalve, dull, nearly smooth or 

 marked by lines of growth. Muscular impressions round, 

 pallial sinus ample. Hinge with small and narrow primary 

 teeth, one or two in each valve ; no lateral teeth ; spathu- 

 late triangular fulcra in each valve with connecting carti- 

 lage. Ligament small, narrow, partially external. 



Animal compressed, oblong or suborbicular ; mantle 

 open, its margins distinctly denticulated. Siphonal tubes 

 long, separated throughout, their orifices plain. Foot large, 

 linguiform, compressed. Labial palps large and trian- 

 gular. 



