48 SYNOPSIS OF THE CHARACTERS OF THE 



This genus lias been formed to include a number of fossil shells of the older rocks, hitherto classed with 

 Sanguinolaria. The latter shells have the dorsal and ventral margins curving towards each other posteriorly; 

 formino- a submucronate, beak -like termination, to the posterior end, while, on the contrary, the dorsal and ven- 

 tral margins of the present shells are nearly parallel, so that the posterior end is as wide, or wider than the 

 other parts of the shell ; they are also much more gibbose, and have no posterior fold. 



Sanguinolites ANGUSTATUS. Phil. SP. 

 • Sanguinolaria angustata. Phil. Geol. York. 



Sp. Ch. — Nearly four times as wide as long; posterior end subtruncate, separated from the body of the 

 shell by a distinct diagonal ridge from the beak ; anterior end short, rounded ; surface with coarse, transverse 

 sulci ; the posterior triangular space nearly smooth. 



This shell is nearly flat, very much elongated transversely ; the hinge-line and front margin are nearly pa- 

 rallel ; length seven lines, width one inch eleven lines. 



Sanguinolites arcuatus. Phil. sp. 



Sanguinolites arcuatus. Phil. Geol. York. 



Sp. Ch. — Transversely elongate, gibbous; posterior, dorsal margin convex; ventral margin nearly parallel 

 to the dorsal, concave; surface smooth, with irregular lines of growth. 



This remarkable shell seems more closely allied to some of the terebrating Modiolce or Lithodomi, than to 

 Sanguinolaria. I have not seen specimens perfect enough to give the proportional measurements. 



Sanguinolites coNTORTus. M'Coy. (PI. XIX. fig. 3). 



Sp. Ch. — Transversely oblong, twice and a half as wide as long ; beaks very large, tumid ; from whence to 

 the posterior part of the front margin, the shell is obliquely gibbous, but without a distinct ridge ; middle of the 

 shell and posterior side flattened, so as to give rather a twisted appearance to the shell ; anterior side narrow, 

 pointed, rounded, having a lengthened, ovate lunule beneath the beak ; posterior end obliquely truncated ; sur- 

 face smooth. 



This species is wider than the Unio Ansticei, and most nearly resembles the common S. tiimida, from which 

 it differs in having the posterior end broader, and instead of the sharp, straight, diagonal ridge of that sf)ecies, 

 there is a very obtuse, rounded, undefined convexity, so curved as to give a twisted appearance to the whole shell ; 

 the posterior side is never flattened in that species ; in that shell also there are three rounded ridges, from the 

 beak to the posterior end, which do not exist in the present shell, which is further distinguished by its more 

 pointed, lengthened, and compressed anterior side. Length of a small specimen eleven lines, width two inches 

 four lines. The specimen figured was presented by Mr. Newenham of Cork. 



Sanguinolites costellatus. M'Coy. (PI. Y^III. fig. 5). 



Sp. Ch. — Transversely oblong, depressed ; anterior side short, rounded, marked towards the margin with 

 four or five short, flat, radiating ribs. 



This rare species is distinguished from all others by the radiating ridges on the anterior side ; the specimen, 

 although imperfect at the posterior end, is very much elongated transversely, probably three times as wide at 

 long. Length six lines. 



Sanguinolites cuRTUs. M'Coy. (PL XL fig. 1). 



Sp. Ch. — Transversely oval, convex; width rather less than twice the length; anterior and posterior ends 

 nearly equally rounded ; abdominal margin rounded ; no posterior diasronal ridge ; surface of the anterior end, 

 and body of the shell, strongly plicated transversely ; one-half of the ridges disappear on reaching the posterior 

 slope, every alternate one suddenly dilating, so as to form very obtuse, smooth ridges, as they pass over the pos- 

 terior area. 



