CANADIAN FOSSILS. 21 



of the spaces between the pseudambulacra, the structure would be 

 exactly that of the upper surface of Blastoidocrinus. 



From another specimen it appears that there are at least three, 

 if not four or five, basal plates, and their form is remarkable, as 

 they do not rest upon the upper surface of the upper joint of the 

 column, as in the ordinary Crinoids, but have their inner edges 

 turned upwards into the body of the cup, leaving a circular aperture 

 in the bottom through which the column actually penetrates into 

 the interior, nearly if not quite to the top of the visceral cavity. 

 This is so extraordinary a structure that scarcely any palaeontologist 

 at all well acquainted with the organization of the Crinoideae could 

 be brought to believe it without personal inspection of the proofs. 

 The two specimens in which the evidence is exhibited were 

 discovered in two different localities. That represented by figures 

 li, 1^ and IZ, I found in a wall about half a mile west of the village 

 of St. Laurent, on the island of Montreal ; the other, figure 1/n, in 

 a quarry five or six miles east of the village. It is quite clear that 

 they are not portions of the same individual. The St. Laurent 

 specimen is part of an individual split in two from top to bottom, 

 and exposing the interior exactly where the column should be found, 

 if it penetrate through the base to the upper part of the visceral 

 cavity, as above supposed. Such is its position in the specimen, as 

 shewn in figure 11. I at first thought that this might be the result 

 of some accident ; but having soon afterwards found the specimen 

 represented by figures Im and 1;^, where a piece of the column is seen 

 penetrating through the base, I believe it to be the natural arrange- 

 ment. The column is round, with an alimentary canal so small that 

 often the detached joints seem to have no central perforation. I 

 have seen it however distinctly in a great many specimens. The 

 flat faces of the separate joints exhibit strong radiating striae. 

 Thickness of column, two lines ; and of the joints, from one fourth 

 to half a line. 



We often find associated with the remains of 5, carcharicedens some 

 small fossils which appear to be the joints of a pentagonal crinoidal 

 column. I have represented several of these by figures io, Ip, Is, 

 plate 1. They have five concave sides, and usually one end is 

 rounded (see figure Is), and the other generally flat, with five deep 

 grooves radiating from the centre to the angles. In some specimens 

 both ends are rounded ; in many there is no central perforation, but 

 in others there is. These are certainly crinoidal remains, but we 

 .have no means of shewing to what species or genus they belong. 



