CANADIAN FOSSILS. T3 



One specimen shews a portion of tlie ventral side, consisting of 

 numerous small plates, thus resembling the genus Pleurocystites. 



The two large side-plates at the base are obscurely striated trans- 

 versely. The body is one-third longer than wide. The plates are thin. 

 The length of the largest specimen a little more than half-an-inch ; 

 width about four lines. All the characters that can be collected from 

 the specimens are comprised in the above description. They are 

 sufficient to shew that this is a distinct genus, and I propose for it the 

 name oi Ateleocystkes from the G^veekateles, " defective or incomplete." 



Professor Hall has kindly furnished me with some of the printed 

 sheets of his forthcoming Vol. 3 of the Palaeontology of New York, 

 in which he has described a new genus Anomalocystites, from the 

 Lower Helderberg series. The materials in my possession are not 

 sufficient to enable me to refer the above to the New York genus. 



The genera of Cystideee have not usually so great a vertical range 

 as that between the base of the Trenton and the top of the Upper 

 Silurian. Should it be ascertained hereafter that the two genera are 

 identical, this species must be referred to Anomalocystites, which has 

 the precedence. 



Another form belonging to this group has been discovered in the 

 Upper Silurian in England. 



Fig. 4. 



The above wood-cut, fig. 4, represents the structure of the dorsal 

 side as nearly as can be made out from the specimens in the collec- 

 tion. 



The species is dedicated to T. A. Huxley, Esq., F.R.S., of the 

 G-eological Survey of the United Kingdom. 



Locality and Formation. — Trenton limestone, farm of Mrs. Brigham, 

 Township of Hull, near Ottawa. 



Collector. — E. Billings. 



In addition to the nineteen species of Cystideans described in the 

 foregoing pages, there are fragments of two others, which are too 

 imperfect to indicate the genus ; but still sufficiently well preserved 



