96 CONTRIBUTIONS TO CANADIAN PALEONTOLOGY. 



Arthroacantha punctobrachiata, Williams. 

 Plate 13, figs. 1, and la. 



Arthroacantha pundobrachiata, H. S. Williams. 1883. Tran.s. Am. Phil. Soc, April, 



pp. 83 & 80. 

 Rystrkrinus Carpenteri, Hinde. 1885. Annals and Mag. Nat. Hist., Ser. 5, vol. 



XV., p. 157. 



Township of Bosanquet, Mr. .J. Pettit, 1868 : Bartlett's Mills, near 

 Arkona, Rev. Hector OiiiTie and Rev. .J. M. Goodwillie, 1882, and H. 

 M. Ami, 1883. 



In the Museum of the Survey there are five good specimens of this 

 species and there are two also in the Redpath Museum at Montreal. 

 These latter were collected by the Rev. Hector Currie, and were kindly 

 loaned to the present writer for examination and study, by Sir William 

 Dawson. Of these seven specimens five have the whole of the calyx, 

 with portions of the arms, beautifully preserved, but the summit of each 

 is completely filled by a shell of Platyceras dumosum, Conrad, var. rarispi- 

 nuni, Hall. The perforated tubercles to which the moveable spines 

 were attached, are well shewn in each specimen and it is not unusual 

 to find the spines lying alongside of the tubercles. 



In 1883 Prof H. S. Williams published a description of a new genus 

 of crinoids for which he proposed the name Arthroacantha. This genus 

 was shewn to be most nearly related to Hexacrinus, Austin, but to 

 differ therefrom in " possessing a well defined third primary radial 

 similar in size to the second, and from which the free arms abruptly 

 diverge," and from it and " from all other hitherto undescribed crinoids, 

 in the possession of slender, acicular spines which were free from the 

 plates iind were evidently articulated by some means upon elevated 

 pitted tubercles on the surface of the calyx, vault and free arms." The 

 type of this genus was stated to be the A. Ithacensis (Williams) " from 

 the base of the Chemung Grouj) at Ithaca, N. Y.," and this species was 

 described in minute detail, with full measurements of all the parts 

 known, and illustrated with an octavo plate of eight figures. 



On page 83 of the paper in which the genus Arthroxcantha was des- 

 cribed by Profesor Williams the following remarks occur. " In study- 

 ing this genus, I have examined several specimens which agree with 

 the typical form in the general character of the plates and the arms in 

 one case, and possess the pitted tubercles on the surface. The most 

 important among these is the original specimen of a figure issued by 

 the New York State Museum with the name Platycrinus ? punctohra- 

 chiatus. The original is in the Museum of Cornell University. The 



