WHiTEAVEs.] FOSSILS OF HAMILTON FORMATION OF ONTARIO. 97 



name was proposed by Prof. Hall, but, as he informs me, the species 

 was never described. This, with several other undescribed species, 

 was i^hotographed and the plate was privately distributed about 18*72, 

 with name attached, but with no descriptions. The arms, the shape 

 of calyx, and the plates that were preserved, correspond in general 

 with A. Ithacensis, but the tubercles on the calyx plates are finer, more 

 numerous, and the pitting verj"- indistinct, and the basal plates are 

 relatively larger than in the typical specimens of that species. Hence 

 we are led to believe that the Hamilton species is distinct from the 

 Chemung specimens, and even if it were properly described and pub- 

 lished, it is probably safe to regard it as a distinct species. Although 

 the specimen shows no traces of the free spines, the nature of the 

 tubercles leave little doubt of a generic identity with Arthroacantha 

 Ithacensis, and the Hamilton form may be called Arthroacantha puncto- 

 brachiata. In the Museum of Cornell University are two specimens, 

 each a jjortion of the basal disc, which aj^pear to be identical with A. 

 punctobracMata. One is marked Moscow shale, locality not designated ; 

 the other is marked Hamilton Period, Delphi, N. Y. and is on a soft 

 dark shale with specimens of PhoUdops." 



On page SB of the same paper, in reference to A. Ithacensis, we read 

 as follows : " This species differs from the Arth. punctobracMata of the 

 Hamilton group in the more distinct and less numerous tubercles on 

 the surface of the calyx jjlates : the smaller size of the tubercles leads 

 to the inference that the spines were smaller in the Hamilton form ; 

 the calyx plates were apjjarently thicker in the Chemung species, and 

 the second and third radial of the specimen Arth. punctobracMata are 

 higher than those of Arth. Ithacensis." 



The following year, on receipt of a copy of Professor Williams' 

 paper, the present writer came to the conclusion that the specimens 

 now under consideration were referable to A. punctobracMata, Williams, 

 first, because they are from the Hamilton Formation, — secondly, be- 

 cause they agree perfectly with Professor Williams' diagnosis of the 

 characters of the genus, — and thirdly, because they differ from the A. 

 Ithacensis, of the Chemung group, as figured by Williams, in having 

 more numerous and less distinct tubercles on the surface of the calyx 

 plates, with shorter and smaller spines articulated to these tubercles. 

 A similar conclusion had previously been arrived at, on perfectly 

 independent grounds, by Mr. Charles Wachmuth, to whom two of the 

 Canadian specimens had been submitted. 



In 1885 Dr. George .lennings Hinde published a paper entitled 

 " Descriirtion of a New Species of Crinoids, with Articulating Spines," 

 and to this species he gave the name Hystricrinus Carpenteri. The 

 specimens upon which the paper was based were stated to be from the 



