•24 SYNOPSIS OF THE CHARACTERS OF THE 



Bellerophon apertus. Sow. 



Bellerophon apertus. Sow. Min. Con Bellerophon apertus. P//il. Geol. York. 



Casts of the Bellerophon apertus, Sow., such as that figured in the Mln. Con., are very common at Carling- 

 ford ; they are spherical, with the whorls slightly exposed in an umbilicus, which closed when the shell is per- 

 fect; the back is depressed. 



Bellerophon cornu arietis. Sow. 



Bellerophon cornu arietis. Sow. Min. Con. — Bellerophon cornu arietis. P/iil. Geol. York. 



iSy;. CA.— Involute, slightly compressed, carinate; whorls widely separated, entirely exposed; aperture 

 expanded; an acute sinus in the middle of the outer lip. 



I have only seen imperfect specimens of this species; the shell is very thick, and the whorls are disjoined, 

 even when perfect. 



Bellerophon costatus. Sow. 



Bellerophon costatus. Sow. Min. Con. — Bellerophon costatus. P///1. Geol. York. 



Sp. Ch. — Central band convex, undefined; surface with sharp, slender, transverse arched ridges ; umbi- 

 licus small, rounded. 



This species is much narrower than the B. hiulcua, having, in fact, a subcarinated appearance ; the dorsal 

 band is convex, and not defined on the sides by ridges or furrows ; the transverse strise are fewer or farther 

 apart than in the B. hiulcus, which is also wider, and has a much broader, defined band. 



Bellerophon hiulcus. Mart. sp. 



Nautilites hiulcus. Martin, Pet. Derb — Bellerophon hiulcus. Sow. Min. Con. — Bellerophon hiulcus. Phil. Geol. 



York. 



Sp. Ch. — Width of the mouth exceeding the diameter of the shell, central band broad, flat, and defined 

 by a sharp elevated line on each side ; surface sharply striated transversely ; umbilicus very small. 



This is wider in proportion than any of the other sjsecies of Bellerophon ; it is also distinguished by the 

 flat, defined, and very broad keel ; the transverse stria3 are sharp, prominent, and arched, as is usvial in this 

 genus. Diameter two inches, thickness two and a half inches. 



Bellerophon l^vis. M'-Coy. (PI. II. fig. 1). 



Sp. Ch. — Globose, very wide, smooth, band narrow, flat, not prominent, defined on each side by an im- 

 pressed line. 



This species bears some resemblance to the B. hiulcus in general form, but is at once distinguished by 

 its smooth surface and narrower band ; the aperture is greatly expanded at the sides, its width being two and a 

 half times its length ; the umbilicus is so shallow that it can hardly deserve the name ; it is, however, defined 

 on the last whorls by an obtuse keel. Diameter one inch six lines, width of the mouth one inch six lines. 



Bellerophon obsoletus. M'-Coy. (PI. II. fig. 3). 



Sp. Ch. — Globose, slightly compressed towards the back; keel convex, but undefined; surface almost 

 smooth, with crowded, nearly obsolete, arched, transverse strise. 



In general form, and in the obtuse, undefined, dorsal band, this species closely resembles the B. costatus 

 Sow., with which I at first confounded it ; the present shell is, however, distinguished by the absence of the 

 distant, prominent, sharp, concentric ridges of that species, the surface being nearly smooth, marked only by 

 very faint, obsolete, transverse strise. Diameter eleven lines, thickness ten lines. 



