24 

 UNG-TJLATA 



Ancodus (Hyopotamus) biiachyrhtnchcs, Osborn and Wortman. 

 Plate II, figs. 1-9. 



Hyopotamus brachyrhynchus, Osborn and "Wortman, 1894. Fossil Mammals of the Lower 

 Miocene White Eiver beds. Collection of 1892 ; Bulletin Amer. Mus. ISTat. Hist., vol. 

 vi, article vii, p. 220, fig. 6b. 



This genus was not known from Canada prior to the publication of the writer's list of fossil 

 remains from the Cypress hills in the Summary Report of the Geological Survey for the 

 year 1901. Unfortunately, separate teeth are the only evidence that we as yet have of the 

 existence of this artiodactyl in this country during Oligocene timet-. 



A well preserved right upper third molar, fig. 1, belonging to this genus, is included in 

 the collection of 1904, and is thought to be referable to A. brachyrhynchus, Osborn and Wort- 

 man, from the Protoceras beds of South Dakota. In this species there is a greater develop- 

 ment of the cingulum in the upper premolars and molars than in A. americanus, Leidy, from 

 a slightly lower horizon. The cingulum in the Cypress Hills molar is conspicuous, and in this 

 respect as well as in its general proportions this tooth agrees better with the corresponding 

 one of brachyrhynchus than with that of americanus. In the Cypress Hills tooth the mesostyle 

 is prominent in the ectoloph, and apparently more protrudent than in brachyrhynchus ; the 

 protoconule is well defined and throughout the cingulum is moderately developed. 



Measurements. MM. 



Anteroposterior diameter 29 



Anterior transverse diameter 315 



Posterior transverse diameter 26 



Height of paracone 13-5 



Height of protocone 12 5 



Within a very short distance of the above tooth, and at the same level, were found four 

 other teeth that appear to belong to this genus, and are probably referable to this species. 

 These teeth are determined as follows : — a left lower first incisor, a right lower third incisor, 

 a right lower canine, and an upper left third premolar, all figured in plate II. The premolar, 

 fig. 2, is sligh'ly smaller than the same tooth in brachyrhynchus, but is otherwise very similar, 

 particularly as regards the shelf-like, iuterno-posterior expansion of the cingulum, which 

 greatly increases the breadth of the tooth behind. As seen from below, fig. 3, the outline 

 of the tooth is triangular, with the inner posterior angle obtusely rounded. The cingulum is 

 continuous throughout, and is conspicuously prominent internally. 



The lower canine agrees in shape with the corresponding tooth of the Hyopotamus from 

 the Lower Miocene of Ronzon, near Puy-en-Velay (Haute Loire), France, as figured by 

 Kowalevsky in the Philosophical Transactions of the Royal Society of London, 1873, vol. 

 163, pi. XXXIX, figs. 3, 3'. Its crown, viewed from the side, is nearly triangular, sharply 

 pointed above (unworn), with its height slightly in excess of the basal breadth. Its anterior 

 and posterior slopes are sharp-edged, the former curving inward below. The exterior sur- 

 face, fig. 5, is convex, somewhat flattened behind. Internally, fig. 4, it is excavated, with a 

 median vertical rib breaking the general concavity. 



