58 CANADIAN FOSSILS. 



ambulacral grooves, to the angles of the truncated apex, bordered 

 by marginal plates, as in G. multiporus, and furnished near their 

 extremities each with several smaller free arms, or stout pinnulee, 

 articulated in two series ; there are about twelve or fifteen pectinated 

 rhombs, each with a smooth central area, which is not elevated 

 above the surface of the pores, but is quite flat, a character which 

 separates this species from the next. 



Neither the mouth nor the ambulacral orifice has been observed, 

 owing to the imperfection of the specimens. 



The column is short, strongly annulated, and tapering to a point 

 at its lower extremity. The small joints are pentagonal, and present 

 a very remarkable character in the fact, that their angles form five 

 spiral lines round the column throughout its length. The large 

 joints which constitute the annulations of the column appear to be 

 circular ; but none of the specimens are sufficiently well-preserved 

 to shew clearly that they are so. 



The pinnulce are furnished on their ventral sides with minute 

 marginal plates, similar to those of Fleurocijstites. This appears to 

 be one of those species in which the body of the arm was never 

 developed, but only the grooves and pinnulae. 



The detached plates of this magnificent species can be readily 

 distinguished from those of any other crinoid or cystidean of the 

 Trenton limestone by the peculiar star-like appearance produced by 

 the very elevated, sharp, and thin radiating ridges with which their 

 surfaces are ornamented. Although a number of the bodies, many 

 of them with the column attached, have been collected, yet none of 

 them shew clearly that side upon which the mouth is situated. 

 The plates are more regularly alternating than in G. multiporus. 

 This species cannot be identified with the Echino-e?icrinites ajiatina- 

 formis figured by Professor Hall in plate xxix. vol. i. Palceontology of 

 New York. By referring to that work it will be seen, that the 

 triangular spaces upon the plates between the large radiating ridges 

 are strongly striated at right angles to the sides of the plates (see 

 the two figures, ^d and also 4_g-, in the plate cited). In our species 

 these spaces are quite smooth, or only marked by faint lines, which 

 are concentric, and therefore run in a direction at right angles to 

 that of the striae of the New York specimens. Professor Hall's 

 figures do not exhibit any pectinated rhombs; and further, by figure 

 4c it is shewn that the base of E. anatinaformis is composed of two 

 pentagonal and two quadrangular plates ; ours has three pentagonal 

 and one hexagonal basal plate. 



