wHiTEAVEs.] FOSSILS OP HAMILTON FORMATION OF ONTARIO. 101 



writer states that the latter " has the same a-eneral form and the same 



o 



arm formula, but the basals are less deep and have around the column, 

 at a level with the lower plane of the calyx, a prominent rim, and its 

 ornamentation consists of numerous ridges arranged in triangles icithout 

 tubercles, and these outer ones enclose two smaller triangles." 



Columns of Dolatocrinus. 

 Plate 12, figs 4, 4a. 



Portions of the column of one or more species of Bolafocrinus were 

 collected by Mr. J. Pettit, in 1868, in the shales of the Hamilton Group 

 of the township of Bosanquet. 



These consist of groups of from two to ten or more joints, which are 

 circular in outline and depressed at the sutui'es, which are sometimes 

 minutely crenulated. In the centre of each of these groups, and 

 superimposed upon two or three joints, there is a prominent but still 

 rather narrow ring, which at equal distances apart bears three lami- 

 nar expansions, which are flattened at a right angle to the joints on 

 which they ai'e placed, but in a direction parallel to the axis of the 

 column. These laminar expansions are triangular in outline, in the 

 only specimen in which their margin is unbroken, their bases are as 

 broad as the cluster of joints of the column of which they form a part 

 is high, and they project from it to a distance of as far as six milli- 

 metres. The central canal is very large and circular in outline. 



Megistocrinus rugosus, Lyon and Casseday. 



ocrinus rugofus, Lyon and Casseday. 1859. Am. Joum. of Sc. and Arts, 

 Vol. xxviii, p. 243. 



Near Thedford, Eev. J. M. Goodwillie, 1882: one specimen, which 

 has been identified with this species hy Mr. Charles Wachsmuth. 



Megistocrincs, Sp, Indt. 



Plate 13, figs. 2, 2a, 2b. 



A specimen which Mr. Wachsmuth thinks is probably the central 

 dome plate of a large Megistocrinus, was collected by the Eev. Hector 



