90 CANADIAN FOSSILS. 



radiations mark the margin as there are ossicles, and the centre of 

 the flat disk is occupied by a star of about eight narrow rays, with a 

 central depression. All of these markings are obscure, but were still 

 capable of demonstration in the specimen (unfortunately since lost, 

 after an accurate drawing had been taken). 



The margin is peculiarly deep and raised like a rim all round ; the 

 outer half of the ossicles, being deprived of radiating ridges, combine 

 to form a smooth channel. The deep-set annular pits shew on the 

 cast as projecting rings with a central depression. 



Locality. — May-Hill Sandstone of Prof. Sedgwick (Upper Llando- 

 very Rock, Murchison), Presteign, Radnorshire, South Wales. 

 Found by J. E. Davies, Esq., F.G.S. 



Regarding the affinities of the fossils, the choice seems to be 

 between Star-fishes and Cystidese. 



At first sight of the more perfect evidence thus brought together — 

 for neither the Canadian or British specimens are complete without 

 the other — the impression certainly was, that we had here a truly 

 circular Star-fish, an extreme form of what is so often approached 

 by some of the Gonialites of the chalk formation. We have figured 

 one (figure 10) to illustrate this comparison, where the marginal 

 ossicles of the disk and of the rays are so much alike, and the latter 

 much shortened as to present nearly a circular outline. 



In the loosely reticular skeleton of the disk there is an addi- 

 tional character, very common in Star-fish, but rare in Crinoids or 

 Cystidege. Against this supposition there is the peculiar excavation 

 of the marginal ossicles, not for the attachment of large marginal 

 spines, such as Goniaster and other star-fishes often exhibit on a small 

 scale, but forming a hollow space, covered over with closely plated 

 ossicles. 



The discovery of the long tube, fig. 2, b, c, made (during the etch- 

 ing of the specimens) by our valued friend, Mr. Sowerby, threw still 

 further doubt on this explanation. It appears as if continuous (though 

 the connection cannot quite be traced,) with the marginal tesselated 

 portions {a, a), and if this were the case there would be a channel 

 running along the outer margin of the disk, and thence out freely at 

 one end, a structure incompatible with that of any known Star-fish, 

 or indeed any Echinoderm whatever. If on the other hand compa- 

 rison be made with certain known forms of Cystideae, although the 

 reticular structure of the disk is abnormal, yet in the arrangement of 

 the marginal ossicles there is a not indistinct resemblance to such 

 forms of Cystideae as Pseudocrmites (fig. 12), or perhaps still nearer to 

 the Canadian form Amygdalocystites, described by one of the authors. 



