20 



A dermal scute, fig. 25, from Bone coulee, possibly referable to this species, may be men- 

 tioned here. It is quadrangular in shape, flat, longer than broad, and broadest behind, with 

 straight sides, and a convexly curved, sharp-edged posterior margin. It attains a maximum 

 thickness of O-o mm. in front and thins gradually to the rear. No overlapping surfaces are 

 seen. Above it is finely tuberculated, the turbercles being distinct from each other, and cloee 

 set, about three in a space of 1 mm. A well defined median ridge is developed in the 

 direction of its length. This scute diflfers from those of this species described by Cope, in that 

 it is keeled, and the granulation, apparently, more distinct. 



Ogmophis compactus, Sp. nov. 

 Plate I, figs. 26-30. 

 Ophidian vertebrce, Lambe, 1905. Geol. Survey of Canada, Summary Report for 1904, p. 366. 

 Four dorsal vertebra apparently belonging to the same species were found separately. 

 They are all of different sizes, and, probably, are from different individuals. The maximum 

 breadth is across the zygapophyses, which are broadly expanded laterally ; it apparently 

 exceeds the maximum height (unobtainable on account of the abrasion of the neural spine in 

 all the specimens) and greatly exceeds the length measured so as to include the pre- and 

 postzygapophyses. A marked character is the shortness of thq centrum. The cup is wider 

 than high with a well defined sharp rim, and is directed very slightly downward. The ball is 

 as slightly inclined upward. The zygosphene is broader than the neural canal is -fride, and has 

 a plane upper surface, and a straight sharp front margin that sUghtly overhangs the upper 

 rim of the cup. The neural spine starts as an angular ridge behind the upper surface of the 

 zygosphene. The neural canal is subtriangular in cross section, the angles being rounded 

 with the apical one the most obtuse ; its sides are slightly incurved. A low rounded ridge 

 occupies the centre of the floor of the canal longitudinally, corresponding in shape with the 

 hypapophysial keel of the lower surface of the centrum. An angular interzygapophysial 

 ridge is feebly developed, the surfaces above and below the ridge being shallowly concave. 

 The front margin of the neural arch between the postzygapophyses is, in outline as seen from 

 above, deeply emarginate, restricting the space available for the base of the neural spine. The 

 facettes of the zygapophyses and of the zygosphene and zygantrum are inclined at a slight angle 

 to each other, those of the zygapophyses being the less removed from the horizontal. The costal 

 tubercle is not prominent ; its articular face in all the specimens is a little worn, hut sufficiently 

 well preserved to show that it is single. Its face is higher than broad, and is directed obliquely 

 outward and downward from beneath the prezygapophysis at a level corresponding with that 

 of the cup. In the largest vertebra (No. 3) the articular face is seen to be convex above and 

 slightly concave below posteriorly. A rounded ridge is developed near the base of #ie 

 tubercle, and passes backward almost to the side of the ball at its mid-height. This ridge 

 leaves a longitudinal depression on either side of the hypapophysial ridge which passes from 

 the ball to the cup, and is well rounded and distinct but not prominent. There are slight 

 variations in the above vertebrae but their general proportions are similar. The vertebra 

 figured on plate I is No. 2 of the table of measurements given below. 



Measurements in MM. 



Length of 

 centrum. 



No. 1 4-3 



No. 2 50 



No. 3 



Nq. 4 4-3 



