Sir W. Daivson — The Animal Nature of Eozobn. 443 



The pes is pentadactyl, and the gait was probably semiplantigrade, 

 like that of many of the recent viverrines. The remarkable pecu- 

 liarities of Hycenodon may, as Filhol has suggested, perhaps find 

 their explanation in the aquatic habits of the animal. 



The structure of the European species of this genus is not nearly 

 so completely known as is that of the American. In dentition and 

 skull structure the two groups of species are nearly identical, and 

 probably the characters of the rest of the skeleton corresponded as 

 closely. In two points, however, the European forms, so far as 

 they are known, deviate from the American : (1) in the presence of 

 an alisphenoid canal, and (2) in the formation of a scapho-lunar 

 bone in the carpus by the coalescence of the scapboid, lunar, and 

 central, which in the American species remain permanently separate. 



This is hardly the place to enter upon a discussion of the relation- 

 ships and phylogenetic descent of Hijcenodon. It may be mentioned, 

 however, that the problem is much modified by the discovery of 

 Hycenodon in the American Upper Eocene (Uinta beds), recently 

 announced by Osborn and Wortman. 



Geological Museum op Princeton University. 

 August 12th, 1895. 



III. — Eeview of the Evidence for the Animal Nature of Eozoon 



Canadense. 



By Sir William Dawson, K.C.M.G., LL.D., F.R.S., etc. 



I. Historical and Stratigraphioal. 



THE writer of these notes had hoped to have been able long ago 

 to let the vexed questions respecting Eozoon repose in peace 

 in so far as he was concerned, and he is now induced to offer 

 a short summary of the evidence in the case only with the view of 

 correcting some misapprehensions that seem to have arisen in regard 

 to points well established, and whicli, independently of any question 

 as to the nature of Eozoon, belong to the certain data of geology. 

 These misapprehensions lead to the confounding of the structures 

 originally discovered by Logan with things in no way related to 

 them, and from which they had been clearly distinguished by my 

 own original studies, and by those of Hunt, Carpenter, and Rupert 

 Jones. New facts relating to pre-Cambrian life have also been 

 coming to light from time to time, and many of these are connected, 

 either directly or indirectly, with the evidence respecting Eozoon. 



As early as 1858, Sir William Logan had begun to suspect that 

 the Stromatoporoid forms collected from the great Laurentian lime- 

 stones in different parts of Canada must be of organic origin, and 

 he ventured to mention them as possibly of this nature at the 

 meeting of the American Association in 1859, and in his General 

 Eeport on the Geology of Canada in 1863. The evidence on which 

 he relied was their occurrence only in the limestones, their similarity 

 in form and general structure to the Stromatoporse, or " Layer- 

 Corals " of the Paleeozoic, and the circumstance that, while the 

 forms and structures seemed to be identical, they were mineralized 



