WHITEAVES.] FOSSILS OF HAMILTON FORMATION OF ONTARIO. 403 



PTEROPODA. 



COLEOPKION (?) TENUIS, Hall. 



Cokoprion(?) tenuis. Hall. 1S79. Pal. N. York, vol. V., pt. 2, p. 184, pi. 32 A, figs. 1 

 and 2. 



" In shales of the Hamilton group, associated with Tentaculites hellulus 

 at Arkona, Ontario, C. W." Hall {op. cit.). For "Arkona," in this 

 quotation, read Bartlett's Mills, near Arkona, — where the species is not 

 very uncommon; and it is most likely that Tentaculites bellulus was 

 written inadvertently for T. attenuatus. 



Hyolitiies aclis, Hall. 



Hmlithes aclis. Hall. 1876. Illustr. Devonian Fossils ; Pteropoda, pi. 27, figs 5, 6, 7, 

 10 & 11. 



]87!l. Pal. N. York, vol. v., pt. 2, p. 197, pi. 32, figs. 22-30 ;& pi. 

 32 A, figs. 23-25. 



Bartlett's Mills, in the "Lower third of the section," C. Schuchert, 1895 : 

 a fragment, about six millimetres in length, of the pointed apical end of 

 a specimen, which is identified with this species by Mr. Schuchert. The 

 specimen, which the writer has examined, is No. 26,491 of the United 

 States National Museum Cat.ilogue of Invertebrate Fossils. 



CEPHALOPODA. 



Orthoceras. 



All the Orthooerata from the Hamilton formation of the province that 

 the writer has seen are mere casts of the interior of the shell, with not a 

 vestige of the test preserved, and the small species are represented by very 

 fragmentary specimens. Under these circumstances the following pro- 

 visional arrangement of the species is suggested. 



A. Shell large. 

 A. 1. Chamber of habitation apparently much longer than the septate portion of the shell. 



Orthoceras Ana.x, Billings. 



Orthoceras Amix, Billings. 1870. Canad. Nat. and Geol., vol. VII, (N. S.), )>. 2.38. 



The original description of this species, which is the only one that has 

 been published, is as follows. " Shell about two feet long and from three 

 to three and a half inches in diameter at the aperture. Septa from six 

 to eight in a length of two inches, where the diameter is eighteen lines. 



