CANADIAN FOSSILS. 31 



Carabocrinus radiatus, Billings. 

 Plate II. Figures da-3e, 



(C. BADiATUS, Report Geological Survey of Canada, 1856, page 276.) 



Description. — Cup, globose, rather broader at the margin than it is 

 high ; base, broadly rounded ; surface, covered with strong rounded 

 ridges, which radiate from the centres of the plates ,• arms, short, 

 three times divided ; column, round and slender, composed of alter- 

 nately projecting thin joints. From the centre of each sub-radial 

 plate two principal ridges ascend diagonally to the bases of the two 

 arms on both sides ; two others radiate to the centres of the two 

 sub-radials on either side ; and thus a series of triangles is formed 

 round the upper half of the cup. In a similar manner ridges extend 

 from the centres of the sub-radials to the centres of the basal plates, 

 thus constituting another set of triangles in the lower half. Within 

 each triangle, both in the upper and lower halves, are contained two 

 or three smaller triangles, one within the other. In consequence of 



this arrangement, the ridges appear to radiate in groups of three or 

 four. 



Each arm-plate supports in its centre a small but stout pentagonal 

 second radial plate, from the upper sloping edges of which spring 

 two short round arms, which divide again at the second joint ; these 

 branches are again divided once or twice above. Height of the 

 largest specimen, one inch ; diameter at half the height, fourteen 

 lines. Specimens are in the collection of all sizes, from three lines 

 to twelve in diameter. 



Explanation of FiauREs. Plate II. 



Figure 3a. View of the anterior side, shewing the azygos inter-radius. 

 " 3&. Base of the same specimen. 

 " 3c. Posterior side of a different specimen. 

 " 3d. Ventral surface of a small individual. In the centre of the lower side 



of the figure is the mouth, and directly above it the small anal 



aperture. 

 " 3e. Ventral surface of a larger specimen, shewing obscurely the five 



ambulacral grooves. The three round darkly-shaded spots appear 



to be apertures accidentally produced. 



For the fine specimen represented by figures 3a and 3b, we are 

 indebted to Mr. Charles Wright, of Hull, Ottawa. 



Locality and Jormation. — Trenton limestone ; City of Ottawa. 



