WHITEAVE8.] FOSSILS OP HAMILTON FORMATION OP ONTARIO. 10" 



about two-thirds the length of the radials, from which it would seem 

 that the radials in Professor Hall's species are not nearly so deeply cleft 

 as they are in the Canadian sjtecimens. 



By whatever name thej' may eventually be known, the Thedford 

 specimens now under consideration differ from the genus Pentremites, 

 as recently restricted by Etheridge & Carpenter in their " Catalogue of 

 the Blastoidea in the British Museum," in the fact that only the inter- 

 radial on the anal side is visible in a side view. In this particular, as 

 well as in the fact that the posterior spiracles are confluent with the 

 anus, they resemble Troostocrinus as defined in the monograph just 

 cited, but their base is not long and tapering, and upon the whole they 

 seem to agree best with the characters of Fentremitidea as expressed in 

 the same volume. 



XucLEOCRiNUS ELEGANS, Conrad. 

 Plate 14, fig. 2. (Summit plates only.) 



Xuckocrinus elegans, Conrad. 1842. Journ. Ac. Nat. Sc. Phil., vol. VIII., p. 289, 



pi. 15, fig. 17. 

 " " Hall (as of Conrad). 1862. Fifteenth Rep. ^^ York St. Cab. 



Nat. Hist., p. 147, pi. 1, figs. 14 and 15. 

 Nvjcleocrinm lucina ? Hall. Montgomery. 1881. Can. Nat. and Geol. (X. S.) 



vol. X., p. 80, with three woodcuts. 

 Nucleocrinus Canadensis, ^Montgomery. lb., p. 83. 



Elseaainvs lucino, HaU, var. Canadensis, Mongomery. Etheridge and Carpenter. 



1886. Cat. Blast Brit. Mas., p. 36, pi. 18, fig. 19. 



Near Thedford, Eev. Hector Cui-rie, 1877-82 : five specimens. 



These differ slightly from typical specimens from the State ot New 

 York, in being not quite so globose in their contour. Judging from 

 diagrams forwarded by Mr. Wachsmuth there would appear to be some 

 minor differences in the shape and number of the summit plates in 

 examples from the two localities, but as the sutures between these 

 plates are nearly always difficult to define, these supposed differences 

 may be more apparent than real. In each of the Canadian specimens 

 the summit plates are preserved, and these, as represented in the figure 

 on plate 14, appear to be seven in number, viz., one j-ather large and 

 somewhat excentric central or sub-central plate, which is partly 

 surrounded by four large and two small proximal^. In the New York 

 specimens, the lower portion of the central or sub-central plate is 

 divided transversely by a suture in such a manner as to separate from it 

 an eighth and distinct anal plate, which is pentagonal in outline, and 

 of which suture or plate no trace has yet been detected in the Canadian 



September, 1887. " 



