57 



The Cypress Hills fragment of lower jaw is from the middle of the left ramus, and holds 

 one tooth, the first molar. Anterior to the tooth is part of the alveolus for the fourth pre- 

 molar, and hehind it the alveolus for the second molar, and the remains of that for the posterior 

 or third molar. The tooth is only moderately worn, and has reached the stage of wear shown 

 by Matthew in his figure 8 B. Of the three fossettes in the worn surface of the crown, the 

 anterior one is closed internally, a slight inflexion of the enamel remains to the posterior one, 

 but there is still a very decided inflexion to the median one. When further worn the 

 posterior fossette becomes complete internally, and later the median one also. The crown 

 of this molar measures, antero-posteriorly 2-25 mm., transversely 2'20 mm. The full depth 

 of the ramus is not preserved, but enough of the bone remains to show that the jaw was deep. 



Matthew places the species with some doubt in the Castoridte. It is interesting to find 

 this small species included in the 1904 collection, thereby adding to the number of species 

 common to the faunas of the Cypress Hills and Pipestone Springs Oligocene beds. 



Locality : — Bone coulee, Cypress hills, Province of Saskatchewan. 



EuTYPOMYS PARVUS, Sp. UOV. 



Plate VI, figs. 1 and 2. 



A single molar represents this species. In the Summary Report of the Geological 

 Survey for the year 1904, the writer specially mentioned this tooth as being worthy of notice 

 on account of the large number of isolated enamel loops or lakes present in the worn sur- 

 face of the crown, and in a foot-note, added whilst the report was being printed, the opinion 

 was expressed that it was probably referable to Matthew's then newly established genus 

 Eutypomys. 



The Cypress Hills tooth, thought to be vhe lower third molar of the left side of the jaw, 

 closely resembles, in tooth pattern, the teeth of E. thomsoni, Matthew, the type species of 

 the genus* from the Oligocene (Lower Oreodon beds of the White River formation, Cheyenne 

 river) of South Dakota. It is considerably smaller than the lower teeth of the type, and indi- 

 cates a proportionately smaller animal. 



Seen from above the crown is subtriangular in outline, the transverse diameter in front 

 being greater than behind ; the antero-posterior diameter exceeds the maximum transverse 

 diameter. A view of the worn surface of the crown is given in plate VI, figure 2, in which are 

 shown the numerous isolated lakes characteristic of the genus. In all about twenty lakes are 

 seen. The tooth is constricted behind its mid-length exteriorly, the crown being well rounded 

 and tumid on each side of the constriction or valley, in which are three or four shallow infold- 

 ings of the enamel below the level of the worn surface. On the inside, at mid-length, the 

 crown is slightly inflected above, but the decided constriction of the external surface is want- 

 ing. The tooth is two rooted, the anterior fang being much the stouter of the two. The 

 anterior surface of the crown is flattened, and has the appearance of having been preceded 

 by a tooth in front. Posteriorly, however, the surface is rounded, as if no tooth pressed 

 against it from behind ; these considerations, together with the somewhat triangular shape 

 of the tooth, suggest its being the last of the series. 



*Notice of two new 'genera ot Mammals from the Oligocene of South Dakota ; Bulletin Airier. Mus. Nat. Hist., vol. 

 XXI, p. 21. 



12529—8 



