CANADIAN FOSSILS. 81 



This genus differs from Protaster as described by Mr. Salter in the 

 Annals and Magazine of Natural History, November 1857, in the 

 following particulars : — 



1. Protaster has a well-developed disc. 



2. It has also the pores outside of the ambulacral ossicles. See 

 Mr. Salter's fig. 4c, in the article above cited. 



3. The same fiigure shows that the oral plates of P. Miltoni are 

 formed of two of the ambulacral ossicles, instead of two of the 

 adambulacral plates. 



These differences are too great to admit of our species being at all, 

 unless very remotely, allied to Protaster. 



VI. T^NiASTER SPiNOSus, Billings. 

 Plate X. Fig. 3«, 36, 3c, U. 



(Falmocoma spinosa, Geological Survey of Canada^ Report^ 1856, page 292.) 



Description. — The specimens collected are about seven lines in 

 diameter ; the rays linear-lanceolate, one line in width at the base, 

 and covered at the sides with numerous small spines. 



In the view of the enlarged specimen (pi. x. 36), the ambulacral 

 ossicles appear in some places to alternate with each other, but this 

 is owing to a distortion. Those on one side of the furrow are opposite 

 those upon the other. The adambulacral plates are elongated, and 

 so placed that the outer extremity of the one lies upon the inner 

 extremity to the next. The rays are flexible. 



Explanation op Figures. Plate X. 

 Figure 3a. — Ventral view of a small specimen. 

 3&. — The same enlarged. 



3c. — Another specimen, with the rajs bent upwards. 

 M. — The same enlarged. 



Locality and Formation. — Falls of Montmorency, Trenton limestone. 

 Collector. — E. Billings. 



VII. T^NIASTER CYLINDEICUS, BillingS. 



Plate X. Figs. 4a, 46. 



{Pal(Bocoma cylindrica, Geological Survey of Canada, Report, 1856, page 292.) 



Descrijytion. — About an inch and a half in diameter or a little more ; 

 rays sub-cylindrical, regularly rounded on the upper side, flattened 

 on the lower, covered aboVe with spines ; about a line in width at 

 the base, and tapering to an acute point. 



