56 



The inner face of the crown is not strongly tumid as in Sciurus typically, but approaches 

 the marginal ridge as a moderately convex slope, in contrast to the other faces, which contract 

 toward the base. The anterior cross crest is formed of two distinct cusps, recalling the sub- 

 division of the crests described by Matthew in Sciurus {Prosciurus) vetustus*. A minute 

 style occurs in the marginal ridge external to the posterior fossette, breaking the continuity 

 of the ridge to a slight extent. No style is present at the outlet of the median enamel 

 inflexion. 



From the above description it will be seen that the tooth pattern implies a near approach 

 to Sciurus, but the radical differences apparent preclude its definite reference to that genus. 

 The comparative prominence of the marginal ridge in front and behind is probably a primitive 

 character. 



Measurements of crown of type specimen: — Antero-posterior, 2 - 30 mm., transverse 

 diameter, 2-70 mm. 



Locality : — Bone coulee, Cypress hills, Saskatchewan. 



Ischyromys typus, Leidy. 



Plate VIII, fig. 18. 



A slightly worn molar is referred to this species described, originally, in 1856, from the 

 Oligocene of Nebraska. The Cypress Hills tooth is apparently a second lower molar from the 

 right side, and was mentioned in the writer's preliminary list of species contained in the 1904 

 collection (Summary Report for 1905) as probably referable to this species. Its tooth pattern 

 agrees fairly well with that of the corresponding tooth, figured by Leidy, in his " Extinct 

 Mammalian Fauna of Dakota and Nebraska,'' 1 1869, pi. XXVI. In size the Cypress Hills 

 tooth is slightly smaller. The antero-posterior diameter of the crown measures 3 mm. and is 

 about equal to the transverse diameter. 



Bone coulee, Cypress hills. Collection of 1 904. 



Cylindrodon fontis, Douglass. 



Plate VIII, figs. 19, 20. 



Cylindrodon fontis, Douglass, 1901 . Fossil Mammalia of the White River beds of Montana ; 

 Trans. Amer. Philos. Soc , vol. XX, p. 15, pi. IX, figs. 9, 9a. 



Cylindrodon fonlis, Matthew, 1903. The Fauna of the Titanotherium beds at Pipestone 

 Springs, Montana; Bulletin Amer. Mus. Nat. Hist., vol. XIX, article VI, p. 212, figs. 

 7 and 8 A, B, C, D. 



Douglass established this genus and species on two parts of right mandibular rami, with 

 well worn teeth, from the Pipestone beds (Oligocene), near Pipestone Springs,in south-western 

 Montana. The variation of the tooth-pattern through wear has been worked out by Matthew 

 from a series of lower jaws, and an upper jaw, from the same locality. 



In the writer's provisional list of the fauna of the Oligocene beds of Cypress hills, as 

 represented by the collection of 1901, part of a left mandibular ramus was referred to a species 

 of Steneofiber distinct from S. nebrascensis, Leidy. This specimen is now seen to be properly 

 referable to Cylindrodon fontis, Douglass. 



* The Fauna of the Titanotherium beds at Pipestone Springs, Montana, 1903. 



