CANADIAN FOSSILS. 49 



The right anterior ray consists of three joints, the first equal in 

 length to the other two, and with one of its angles truncated where 

 it is in contact with the azygos inter-radial. The left anterior ray 

 has four joints, the second being the longest, and having one of its 

 angles truncated to support the inter-radial. The other three appear 

 to consist each of four equal joints. The upper joint of each ray 

 is pentagonal, and supports two secondary rays, which continue 

 single to their extremities. The azygos inter-radial is oblong, higher 

 than wide, five-sided, two of the sides meeting to form an obtusely- 

 pointed lower extremity, which rests wedge-like between the trun- 

 cated angles of the first joint of the ray upon the left, and the second 

 joint of the ray on the right ; its upper bide is horizontal and supports 

 another plate, which is probably the base of a proboscis. The 

 secondary rays, ten in number, consist each of a series of oblong, 

 quadrangular joints, usually one line in length and two-thirds of a 

 line in breadth. 



There is a row of long pinnulse upon each of the inner margins of 

 each ray; they rise upwards, nearly parallel with the rays, instead 

 of projecting at nearly right angles, as in other species. The column 

 is round and smooth at the base of the pelvis, below which it tapers 

 and becomes very slender at the distance of one or two inches, then 

 slightly larger and composed of compressed globular joints, the 

 rounded edges of which, to the eye, present a bead-like appearance. 

 The longest column seen with the head attached was fifteen inches ; 

 and, as it was broken ofi" below, it had been probably several inches 

 longer. The diameter is usually somewhat less than a line, and there 

 are about seven joints of equal size to two lines in length. The 

 smooth, slender, upper portion of the column, near the base of the 

 cup, is generally half a line or a little more in diameter, expanding 

 to twice or three times this size at the base. 



H. simplex, according to Professor Hall, has the column at the 

 base of the cup pentagonal, but is otherwise closely allied to 

 H. Canadensis. (See description of H. simplex in the Palaeontology 

 of New York, volume i., page 280.) 



Explanation op Figures. Plate IV. 



Figure 5a. A specimen with part of the column attached. 



" 56. Portion of the column, enlarged. 



" 5c, Anterior side of a different specimen. 



" M. A specimen which has the pinnulse preserved. 



Locality and formation. — Trenton limestone, Ottawa and Montreal. 



D 



