19 



This species is peculiar on account of the extreme narrowness and thickness of the 5th 

 costal plate. The surface of the carapace bore a distinct pattern of grooves which were, 

 anteriorly at least, arranged concentrically within the boundaries of the epidermal shields. 



Triontx leucopotamicus. Cope. 



This species was described by Cope in 1891*. The material on which it is based consists 

 of part of a costal bone from Bone coulee, Cypress hills, (Mr. T. C. Weston's collection of 1884) 

 and some well preserved fragments from the White buttes, Dakota. 



In the collection of 1904 from Bone coulee are a number of fragments of shell, prin- 

 cipally broken costals, that are evidently referable to this species. 



Other fragments may be assignable to T. punctiger, Cope, from the Oligocene (White 

 River) of South Dakota, but the material is too poor to admit of a satisfactory determination. 



SQXJAMATA. 



Peltosaurus granulosus, Cope. 



Plate 1, figs. 23, 24 and 25. 



Peltosaurus granulosus, Cope, 1873. Palteontological Bulletin, No. 15, p. 5. 



" " Cope, 1874. Annual Report XJ. S. Geol. and Geog. Survey Terrs. 



for 1873, p. 513. 

 Peltosaarus granulosus, Cope, 1884. The Vertebrata of the Tertiary Formations of the 



West, U.S. Geol. Survey Terrs., vol. Ill, p. 773, pi. LX, figs. 3-11. 

 Peltosaurus granulosus, Lambe, 1905. Geol. Survey of Canada, Summary Report for 1904, 



p. 366. 



With this species are identified part of a left dentary (fig. 23) and the posterior half of a 

 right maxilla (fig. 24), in both of which specimens a number of the teeth are preserved. A 

 worn portion of a second dentary from which the teeth have been abraded, probably, also 

 belongs to this species. 



The type specimens described by Cope are from the Miocene of north-eastern Colorado ; 

 the Canadian specimens were obtained by the writer from the Oligocene beds of Bone coulee, 

 Cypress hills, in 1904. 



In the dentary shown in figure 23, the teeth are pleurodont, of fair size, chisel-shaped, and 

 apparently in all particulars agreeing with those of the type specimens. There are four 

 of the largest teeth in a space of about 5 mm. The mandibular groove, seen in the inferior 

 surface of the specimen, is of large size, and the dentary canal is well shown, piercing the bone 

 midway between the surface of attachment of the teeth and the exterior surface of the speci- 

 men in which occur a few small foramina. 



In the maxilla there are eight teeth preserved, diminishing in size toward the back. 

 Exteriorly the bone curves slightly outward behind, and above posteriorly is seen the surface 

 for the articulation of the jugal. The teeth correspond in size with those of the dentary. 



The Cypress Hills specimens are smaller than the corresponding bones on which the 

 species is based, but there is no evidence to indicate that they belong to a different species. 



* The species from the Oligocene or Lower Miocene beds of the Cypress hills. Geol. Survey of Canada. Contr. to Can. 

 Palseont., vol. Ill, (quarto), pt. I, p. 5, pi. I, figs. 8 and 1). 



