106 CONTRIBUTIONS TO CANADIAN PAL/EONTOLOGY. 



radials, and occupy nearly their whole area, leaving only a very nar- 

 row rim exiwsed. They are equal in size, similar in shape, and partly 

 divided in the centre by an incomplete septum. Central opening 

 pentagonal or obscurely five-lobed, but shallowly and concavely emar- 

 ginate on the anal side. 



Summit plates, hydrospires, pinnules and column unknown. 



The surface ornamentation consists of exceedingly fine concentric 

 lines, which follow the general contour of each plate. These lines arc 

 always too minute to be seen without the aid of a lens, but ai-e much 

 coarser and more sharply defined in some specimens than in others. 



Dimensions of one of the most pei-fect specimens collected: Height, 

 thirteen millimetres ; maximum bi-eadth, nine and a half mm. ; height 

 of radial, eleven; breadth of radial, five; dejith of sinus of radial, nine 

 and a half 



Near Thedford, Eev. Hector Currie, 1876-82 : nine specimens, most 

 of which are perfect, undistorted and remarkably well-preserved. 



A provisional name has been given to the specimens desci'ibed above, 

 because it is almost impossible to decide whether they are or are not 

 identical with the Pentremites Whitei of Hall, owing to the very 

 peculiar state of preservation of the latter. 



Professor Hall's types of P. Whitei (two of which he has kindly lent 

 to the present writer, for comparison) are all stated to be " crushed" so 

 that "their true form cannot be known." One of the specimens 

 forwarded by Professor Hall has the pinnules preserved on all sides, 

 so that the whole of the interradials and summit characters, as well 

 as the upper halves of the radials, are completely hidden from view. 

 In the other, most of the pinnules are preserved, especially on one 

 side. This latter is the only specimen which shews any of the inter- 

 radials, and in it the writer has failed to find more than one, which 

 ap|icars to be the iiitci'radial on the anal sidfe. Moreover, the char- 

 aclers of this supposed solitary interradial on the anal side in one, 

 and those of the lower and exposed half of the body in both of the 

 ty]iieal examples (jf P. Whitei that the writer has been able to 

 examine, appear to be essentially similar in all resjjccts to those of the 

 corrosj)onding parts in the Canadian specimens. 



But, on the other hand, Professor Hall distinctly states that the 

 intori-udials of P. Whitei are '' comparatively lai-ge and lozenge shaped,'' 

 anil if this is true of any of its interradials other than the one on the 

 anal side, then F Whitei must bo both generically and specifically 

 distinct from the specimens collected by the Eev. H. Currie. Again, 

 in the original description of P. Whitei, the pseudambulacral fields 

 (ambulacra) are said to " extend a little more than half the length of 

 the body,'' and the pseudambulacral areas (or radial sinuses) to occupy 



