134 PROCEKDINGS OF THE ACADEMY OF [1888. 



Surface of tlie radial plates transversed hy coarse radiating ridges 

 of which there are four or five on both sides of the central elevation 

 in each of the radials, surface between the ridges seems to be quite 

 smooth, although so much difficulty was experienced in removing 

 the adherent shale that this point could not be decided accurately. 

 The interradial and inter-axillary plates have less prominent ridges 

 ornamenting their surface. 



Arms long, slender, of nearly equal diameter till near the tip, 

 where they are very gradually tapering to a quite acute termination; 

 surface smooth. Length about six centimeters, pinnules very deli- 

 cate from five to seven millimeters long at the lower portion; rapidly 

 shortening at the tip of the arm. 



Column stout, as thick as the base of the calyx, at that point, 

 from which it evenly tapers as far as it is preserved, which is about 

 twelve centimeters, to one half its diameter at the calyx. Joints 

 with rounded central projections, which are not quite so wide as the 

 joint is long. 



This species differs from 31. carleyi, Hall, wath which it agrees in 

 the general size and contour of the calyx, principally in the surface 

 ornamentation ; it having a smoother surface and more numerous 

 radiating ridges on the radial plates, and they are also thicker than 

 in the former and the base is somewhat wider. 



This specimen is from the upper third of the shale, and is associa- 

 ted on the same slab with the Dendrocfrlnus just described, its column 

 lying across that of the former. This unique slab was found and 

 presented to the author by W. H. Warren Esq. of Lockport, after 

 whom the species is named. 



OrtMs acutiloba (n. sp.) PI. VII, fig. 5. 



Shell bilobate, obversely cordate in outline, apex semi acute. Both 

 valves have a deep and sharp mesial depression thus forming an 

 acute notch in the anterior margin. Hinge line very short, termina- 

 ting in small sloping auricles which are scarcely noticeable when 

 the shell is viewed from the ventral side. 



A profile view shows the ventral side to be strongly convex with 

 the beak of that valve projecting far beyond the other and somewhat 

 outward, while the dorsal profile is sinuous, being slightly concave 

 immediately behind the umbo and convex anteriorly. Length and 

 breadth each five millimeters. 



