CANADIAN FOSSILS. 25 



also five small orifices leading to the interior. The mouth is pro- 

 bably situated near the margin, at the azygos inter-radius. Column, 

 either round or pentagonal. 



This genus belongs to that group of the Crinoideae which includes 

 such genera as Cyathocrinus, Poteriocrinus, Dendrocrinus and Forocrinus, 

 to all of which it is closely allied in structure, but differs in the 

 presence of calycinal ambulacral furrows. 



Pal^eocrinus striatus, Billings. 

 Plate I. Figures 5a, 5b. 



Description. — Cup, oval, gradually expanding from a small base to 

 the width of five lines at the margin of a specimen seven lines high. 

 The plates are depressed convex, and have a small round tubercle in 

 the centre. They are also beautifully ornamented with radiating 

 strise or somewhat sharp,[elevated ridges. One of these extends from 

 the centre of each plate to the middle of each edge, and, crossing the 

 suture at right angles, proceeds straight to the centre of the conti- 

 guous plate. Parallel with these principal ridges are four or five 

 other shorter ones, also crossing the suture at right angles. Those 

 nearest the principal ridge are the longest, and the length gradually 

 decreases towards the angles. Where the ridges cross the suture, 

 there are from three to five of them in the width of one line. 



The only specimen collected shews very distinctly two ambulacral 

 orifices at the bases of two of the arms, and two calycinal ambulacra 

 leading therefrom towards the centre. The other three grooves are 

 indistinctly indicated, but sufficient appears to leave little doubt as 

 to their existence. The arms and column are unknown. 



The plates of this species so closely resemble those of the cysti- 

 dean Falaocystites tenuistriaius, that they can only be distinguished 

 after much practice. The striae on the surface of the latter species 

 are always a little finer and of a nearly uniform size. 



Explanation of Figures. Plate I. 



Figure 5a. Posterior side of a nearly perfect specimen. 



" 5b. Summit of the same, shewing the ambulacral orifices and grooves. 



Locality and formation. — Somewhat common in the Chazy limestone 

 at Caughnawaga and on the Island of Montreal. 



