CANADIAN FOSSILS. 63 



Explanation of Figures. Plate VI. 



Figure la, A specimen with part of the column attached. 

 " lb, Ic. Crushed specimens. 

 " Id. The radix of this species. 



Locality and formation. — Trenton limestone, City of Ottawa, plen- 

 tiful ; also in the upper part of the same formation, around the base 

 of the mountain at Montreal, where the columns are rather common. 



Rhodoceinus microbasalis, Billings. 

 Plate VI. Figure 2. 



(Thtsanoceinus [Rhodoceinus] microbasalis, Rep. Geol. Survey of Canada, 1856, p. 264.) 



Description. — The specimens for which the above specific name is 

 proposed are about five-eighths of an inch in height, and the same 

 or a little more in breadth at the top. They are cup-shaped, and 

 uniformly expanding from the narrow base upwards. The basal 

 plates are so small that they can only be well seen when the column 

 is removed. The rays are keeled, and all the plates of the body 

 exhibit obscure, radiating ridges, somewhat similar to those of 

 Glyptocrinus ornatus, but not so prominent. The column is round, 

 annul ated in its upper and smooth in its lower part. I have not 

 seen either the root or the arms. 



This species is closely allied to R. pyriformis, but diiFers in its 

 much smaller size, in the comparative minuteness of the pelvic 

 plates, and also in the character of the surface. R. pijriforynis is a 

 large, smooth species, but this one has a surface ornamented with 

 stars, only well seen however on good specimens. 



Locality and formation. — Trenton limestone. City of Ottawa. 



Genus Eeteocrinus, Billings. 



Generic characters. — This remarkable genus has no perfectly formed 

 plates. The cup consists of a reticulated skeleton, composed of 

 rudimentary plates, each consisting of a central nucleus, from which 

 radiate from three to five stout processes. Of such plates there are 

 five in the basal series, five in the sub-radial, and five in the radial 

 series. On the azygos side the sub-radial has five processes; the 

 others have four each. 



