50 SYNOPSIS OF THE CIL\RACTERS OF THE 



SaNGUINOLITES RADIATUS. M'Coi/. (PL XIII. fig. 4). 



Sp.Ch. — Transversely oblong, nearly tliree times as wide as long, evenly convex ; dorsal and ventral 

 margins parallel, ends equal, rounded ; surface radiated with about twelve unequal, broad, convex ribs, from 

 the beak to the ventral margin ; anterior and posterior extremities smooth ; no posterior oblique ridges. 



Length four lines, width ten Hues. 



Sanguinolites SULCATUS. Phil. SP. 

 Sanguinolaria sulcata. Phil. Geol. York. 

 Sp. Ch. — Transversely oblong, twice and half as wide as long, convex; posterior end subtruncate, 

 roimded, gaping ; anterior end small, rounded ; surface with large wrinkles on the posterior slope, which divide 

 each into two or three sharp, narrow sulci, on the body and anterior end of the shell. 



This species is almost always found with the two valves together ; the large, posterior wrinkles dividing 

 each into a number of small ones, as they cross over the body of the shell, give a curious character to the sur- 

 face. Length one inch, width two inches five lines. 



Sanguinolites transversus. Forth, sp. 



Sanguinolaria transversa. Portk. Geol. Eep. 



Sp. Ch. — Transversely elongate, lanceolate; width three and a half times the length; beaks very small, 

 close to the anterior end ; anterior end short, rounded ; ventral margin convex ; posterior end narrow, obliquely 

 truncated ; hinge-line nearly as long as the width of the shell ; surface marked with small, faint lines and 

 waves of growth. 



From the drawing given in Captain Portlock's Report, this species has been thought to resemble the 

 S. vetusta, M'Coy ; but when specimens are compared, the species seem quite distinct ; the strise and concentric 

 waves of the former species are fine, and so faint as to be nearly obsolete, while in the latter they form large, 

 rounded, prominent ridges ; and one imvarying character, observable even in a cast, would distingush them, in- 

 dependent of surface, namely, that in the S. transversa the posterior end is considerably narrower than the 

 length from the beak to the opposite ventral margin, while in the S. vetusta it is considerably broader. 

 Length one inch one line, width three inches nine lines. 



Sanguinolites tricostatus. Portk. sp. 



Sanguinolaria tricostata. Portk. Geol. Rep. 



Sp. Ch. — Transversely oblong, nearly three times as wide as long; diagonally gibbous; beaks large, pro- 

 minent ; anterior side very short, rounded ; front margin slightly convex, with a shallow sinus opposite the 

 beak ; posterior side lengthened, obliquely rounded ; a strong ridge extends from the beak to the posterior in- 

 ferior angle ; between this keel and the hinge-hne, are two other strong, rounded, radiating ridges, dividing 

 the posterior slope into three equal, concave spaces ; surface marked with close, fine, transverse strise. 



This handsome species, in general form, resembles the S. titmidus, but the posterior ridges are more dis- 

 tinct, and the regularly striated siu-face at once distinguishes it. Length nine lines, width two inches one line. 



Sanguinolites TUMiDus. Phil. sp. 



Sanguinolaria timiida. Phil. Geol. York. 



Sp. Ch. — Three times as wide as long, very gibbous; beaks large, tumid; a distinct keel runs from the 

 beak to the posterior angle, separating the posterior slope from the body of the shell ; surface smooth ; three 

 obscure, radiating ridges on the posterior side. 



This large species has the beaks remarkably prominent; the surface is smooth, with the exception of a few 

 imbricating lines of growth. Length one inch ten lines, width three inches eight lines. 



