BY JOHN MITCHELL. 



259 



*S^. Char. — Plates : Longer axis between the angular points in 

 the larger plates equals 1 7-20 ninety-sixths of an inch, with a width 

 of thirteen ninety-sixths between 

 the parallel edges is very constant, 

 highly granulated and tubercled, 

 subconvex, edges tirmly attached, 

 sutures distinct; tubercles appar- 

 ently seven on each, one central 

 and the others peripheral, being- 

 placed adjacent to the angles, but 

 this arrangement is only visible 

 upon one or two of the most per- 

 fect plates. The contour of the 

 whole is convex. 



OJjs. — This fossil in size of plates agrees with P. elUpticus, 

 McCoy, froai the Carboniferous of Ireland, but the tubercles are 

 more pronounced and less in number in the former. That 

 it is not a cystidean is plain by the absence of the ridges from 

 the angles to the central point and of the parallel striation so 

 characteristic of the plates of these fossils, as well as l)y the 

 absence of any resemblance of the plates to the pyramidal form. 



Its separation from the Crinoidea seems equally clear by the 

 distinct tuberculation of the plates of the former and by their 

 uniformity of character. 



The plates of the calyx of Platycrinufi are numerous, hexagonal 

 and of varying size ; but they increase rapidly in dimensions 

 towards the base and are void of tuberculation; and thus disagree 

 with the fossil under consideration. 



In the absence of ambulacral and genital plates and other parts, 

 it must be admitted that the determination is not altogether 

 beyond doubt. I therefore refrain from giving it specific rank. 



Zoc— Middle Trilobite Bed = (nVenlock); Yass Beds (David); 

 Hume Beds (Jenkins). Bowning Village, County Harden. 



