CONTRIBUTIONS TO PALAEONTOLOGY. 119 



ANCYROCRINUS SPINOSUS (n.s.). 



Body biturbinate, smaller above; lower part rounded, swelling and 

 sometimes ventricose. Lateral processes four, arranged at regular 

 intervals and at nearly equal height from the base. The central 

 portion above the lateral processes more or less elevated, rounded, 

 and, in the young forms, extremely conical; the summit marked 

 by a scar, but no column has been seen attached. 



Geological formation and locality. Limestone of the Upper Helderberg 

 group : Falls of the Ohio, and elsewhere. 



GENUS PLATYCRINUS ( Miller). 



PLATYCRINUS ERIENSIS { n. s.). 



Body small, cup-shaped : cicatrix for the attachment of column 

 comparatively large, bordered by a thickened rim. Basal plates 

 closely anchylosed, curving gently upwards : radial plates a little 

 wider than high, and the suture marked by a sharp line. The 

 centres of the plates become prominent above the middle, and 

 terminate in a conspicuous articulation which occupies nearly 

 one-third the width of the plate. First arm-joint quadrangular; 

 the second pentagonal, giving a bifurcating arm : arm-joints 

 strong, subangular, thickened at their extremities, and supporting 

 on the upper angles strong jointed tentacula. Surface granulose. 



This neat little species is scarcely more than three-sixteenths of an inch 

 from the base to the origin of the arms, while the arms themselves have 

 been more than three times as long. The strong subangular joints of the 

 arms, and the strong tentacula, are marked characters. 



Geological formation and locality. \i\ the shales of the Hamilton groupie 

 near Hamburgh, Erie county, N.Y. Collected by C. A.. WmiE, 1860. 



PLATYCRINUS EBORACEUS (n.s.). 



Base large, spreading, consisting of three distinct plates, the suture 

 lines marked by a narrow ridge : cicatrix for column attachment 

 of moderate size, prominent, and very distinctly serrated on the 

 edge. Entire surface finely granulose. 

 The width of the basal plates altogether is nearly an inch, while 



the elevation is only about three-fourths of an inch. 



Geological formation and locality. In the shales of the Hamilton group: 

 near York, Livingston county. Collected by C. A. WmiE and R. P. Whit- 

 field, 1860. 



