40 CANADIAN FOSSILS. 



Explanation of Figures. Plate III. 



Figure 5a. View of the left side, shewing the left anterior ray, which has the first 

 and second primary radials included in the cup. 

 " 5b. View of the anterior side. 

 " 5c. The posterior side. 



Locality and formation. — Hudson River group, Charleton Point, 

 Anticosti. 



Dendeocrinus similis, Billings. 



(D. SIMILIS, Report Geological Survey of Canada, 1856, page 267.) 



Description. — Cup, small, conical and sub-pentagonal ; arms, long, 

 three or four times sub-divided, rather broadly rounded on the back, 

 and comparatively stouter than those of any of the above described 

 species. Of the two arms preserved in the specimen examined, one 

 remains single for a distance of two lines and a half, and then divides; 

 there are five joints in the undivided part ; the other arm shews but 

 two joints in the part below the first bifurcation. The column for 

 seven lines below the basal is pentagonal, with round edges and 

 slightly concave faces ; it is composed of alternately thick and thin 

 joints, nine of each in the space of two lines, diameter of column 

 nearly one line ; length of arms sixteen lines, and the diameter at 

 the undivided part nearly a line on the back. 



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



The last three species appear at first sight to be identical, but the 

 moment a magnifying glass is brought to bear upon them, their 

 differences become quite as apparent as those of the large species. 

 In D. acutidactylus the arms are exceedingly thin and sharp on the 

 back above the first division like the edge of a knife, and the column 

 is circular and composed of round edged joints, which at the distance 

 of one-half or three-fourths of an inch become nearly globular. In 

 D. proboscidiatus the column at the base of the cup is pentagonal with 

 the angles so strongly projecting, and the faces so concave that a 

 single joint has the form of a five-rayed star ; the arms, judging from 

 the fragments seen, were very similar to those in D. acutidactylus. 



In D. similis the column is only different from that of D. probosci- 

 diatus by the unequal thickness of the joints, and in being more 

 regularly pentagonal ; its faces are only slightly concave, its arms 

 also are five times thicker. 



