28 



The writer wishes to acknowledge the assistance rendered to him, by Dr. O. P. Hay, 

 of the American Miisetim of Natural History, who by the expression of his views regard- 

 ing the affinities of some of the species of turtles represented in the collections, and by 

 other courtesies, greatly facilitated the work connected with the determination and 

 description of these interesting reptiles. 



In 1901, Mr. L. Heber Cole, of Montreal, acted as assistant in the field, and contributed 

 materially to the success of the expedition of that year. 



The writer is particularly indebted to Professor Henry Fairfield Osborn, Curator of 

 the Department of Vertebrate PaljBontology of the American Museum of Natural History, 

 New York, for his co-operation in the study of the structure, systematic relations and 

 nomenclature, pursued partly in Ottawa, partly in the American Mtiseiim by comparison 

 with the extensive Cope collection. 



PISCES. 



Myledaphus, Cope. 



Ml'LEDAPHUS BIPAKTITUS, Cope. 



Plate XIX, figs. 1 and 2. 



Myledaphus hiparlitus. Cope. 1876. Proc. Acad. Nat. Sci. Philadel., p. 260. 



This species is represented by many teeth found separate in all cases. Their varia- 

 tion in size is considerable, the smallest measuring about 225 mm. on the longer 

 diameter of the crown, whilst the largest collected has a diameter of 9 mm. in the same 

 direction. The proportions of the majority of the specimens are nearly constant. Measure- 

 ments taken from an average sized tooth almost coincide with those given by the 

 author of the species in his original description. In the majority of the specimens the 

 crown is irregularly striated in a direction at right angles to and on both sides of the 

 line dividing it into halves although generally one half has fewer striations than the 

 other. The crowns of some of the teeth are smoother than those of others, a dift'erence 

 due probably to age. 



Measurements of an average sized tooth. 



M. 



Length of tooth • 0055 



Long diameter of crown • 0062 



Short " " " • 0045 



Length of root ■ 0030 



Long diameter of root , ■ 0042 



Short " " •' ■ 0030 



Belly River series, Eed Deer river, 1898 and 1901. 



Dr. Gr. M. Dawson collected a number of specimens on Belly river, N.W.T. (Nos. 40 

 and 41), in 1881, and Mr. Weston specimens in Irvine coulee, near Irvine station on 

 the line of the C.P.E., in 1888. 



