No. 136.] 107 



size equal to that one. The specimens measure from an inch to one and 

 a half inches in diameter, with a length about one-fifth greater. 



Geological formation and locality. In the Upper Helderberg limestone: 

 Clarence Hollow, Stafford, and other places in Western New-York. 



EUOMPHALUS CONRADI ( n. s.). 



Shell discoid. Volutions three or four (rarely preser^«g more 

 than two or three), gradually enlarging from the apex, which 

 is depressed below the plane of the outer volution : inner volu- 

 tions rounded above, gradually becoming depressed, tind the 

 outer one flattened and sloping towards the ventral side, the 

 upper or dorso-lateral edge obtusely angular ; periphery moder- 

 ately convex, sometimes flattened and gradually contracting to 

 the lower side, which is obtusely angular with the base 

 abruptly depressed, forming a wide umbilicus. Aperture some- 

 what quadrilateral ; a short, nearly straight side against the 

 inner volution ; the upper side making a little more than a 

 right angle, while the outer edge makes nearly a right angle 

 with the upper side : the lower side conforms to the upward, 

 bending at the lower outer angle, and, thence following the 

 curve of the umbilicus, is longer than the other sides. 



Shell thin. Surface marked by fine elevated strias of growth, 

 without cancellating striae. 



The fossil has a diameter of two to four inches; but as it usually 

 occurs in the form of casts, the inner volutions are not well preserved : 

 these, at first rounded, gradually become flattened above as they extend 

 from the apex, and the last one slopes from the periphery, giving a con- 

 cave upper surface. In rare instances, the apex of the spire rises nearly 

 to the plane of the outer volutions. 



This species resembles the Euomphalus disjunctus of the Lower Hel- 

 derberg group, but is distinguished by the flattening of the upper side, 

 and the obtuse angles above and below upon the outer volution. It 

 also resembles more nearly the E. trigonalis of Goldfuss; but the outer 

 volution is never so much dilated, nor does our shell exhibit the revol- 

 ving striae represented in the figure of Goldfuss. 



Geological formation and locality. In limestone of the Upper Helder- 

 berg group : in numerous localities in Central and Western New- York. 



