28 CANADIAN FOSSILS. 



Locality and formation. — This species occurs in the Chazy lime- 

 stone, in a quarry about two miles north of the City of Montreal. 

 Exceedingly rare. 



SECTION III. 



CRINOIDE^ OF THE TRENTON LIMESTONE AND HUDSON RIVER GROUP. 



Although in almost every exposure of the Trenton limestone we 

 find remains of the Crinoideae, yet in general they consist of mere 

 fragments, such as joints of the column or the detached plates of 

 the cup. At the city of Ottawa they are found in a better state 

 of preservation, but seldom perfect. Nearly all the species that 

 we have been able to determine were collected at that locality; 

 and as we know, from the researches of geologists in other countries, 

 that these fossils are often confined to limited areas, it appears 

 probable that few of ours will be found elsewhere. 



The Hudson River species are so closely allied to the Trenton 

 that I have not thought it necessary to describe them in a separate 

 section. 



Hybocrinus tumidus, Billings. 

 Plate II. Figures la-le. 



(H. TUMIDUS, Report Geological Survey of Canada, 1856, page 2Y5.) 



Descriptio7i. — Smaller than H. conicus ; sub-globular, the plates 

 tumid in their centres; column, slender and round, composed of 

 thin joints, and tapering towards the base; surface of the plates, 

 obscurely granular ; length of cup, six lines ; breadth at margin, 

 about eight lines; arms, one line broad upon the back, composed of 

 joints one line in length. Although about twenty heads of this 

 species have been collected, none of them are quite perfect. 

 They all are smaller and of a different form from H. conicus. 



