92 PALEONTOLOGY OF NEW YORK. 



Surface marked by concentric, thread-like striae which, for a narrow space, 

 are directed a little forward from the suture to a revolving crenulated 

 carina, and thence make a gentle curve backward to the peripheral band, 

 below which they are again directed forward with a scarcely perceptible 

 curve ; peripheral band tricarinate. The stria; make a single retral curve 

 across the space between the outer carina;, without essential interruption 

 by the central line. 



The summit of the volutions is canaliculate just below the suture-line, and 

 the stria? bending forward from the suture are turned backward as they pass 

 the carina limiting the narrow groove. The striae are distinct and thread-like 

 in character, but not so coarse as in M. Leda, and the spire is less rapidly 

 attenuate. The species is also distinguishable by the canaliculate suture 

 and tricarinate band. 



Formation and locality. In limestone of the age of the Upper Helderberg 

 group, at Cambridge, Ohio. 



MURCHISONIA INTERCEDENS, n. sp. 

 PLATE XXVIII, FIG. 29. 



Shell turreted ; spire somewhat rapidly attenuate above. Volutions about 

 nine in the length of a little over half an inch, angular and rapidly 

 enlarging, the last one ventricose ; the apex imperfect in the specimen 

 described ; the volutions about equally depressed-convex on each side of 

 the peripheral band. Aperture broadly oval, a little longer than wide ; 

 columellar lip extended below and pointed. 



Surface marked by a narrow peripheral band in the middle and on the summit of 

 the volutions, and the spaces above and below by rather strong transverse 

 striae, which apparently cross the upper volutions almost vertically. 



Tbis species has been seen only in the specimen figured, but its general 

 form and the decided angularity of the volutions are sufficient to separate it 

 from any other species of the formations under consideration. The specimen 



