88 CONTRIBUTIONS TO CANADIAN PAL^ONTOLOGT. 



a bristle at the summit, and which, occasionally, arc surrounded by a 

 minute annulus at the base ; and the three keels each have a single 

 series of larger conical tubercles, whose jjointed aj^ices are directed 

 forward. 



In front of the transverse and Y-shaped furrow the carapace is very 

 badly preserved, and the anterior margin with the rostrum is ?jroken 

 oft'. The two lateral and tuberculated I-ceels apjjear to be prolonged to 

 within a short distance of the front margin of the carajjace, though 

 they are somewhat less distinct in front of the transverse furrow than 

 they are behind it. On the anterior side of the furrow the central 

 keel is absent, and the median portion of this part of the carapace 

 bears a number of comparatively large and prominent, distinct and 

 conical tubercles, which are somewhat peculiarly ari'unged. Xext to 

 the farrow, and in advance of it, in the median line, there are five 

 tubercles arranged in two convergent rows of two pairs and an odd 

 one, which, if connected by line-<, would have much the shape of an 

 isosceles triangle, witn its base near to the furrow. Between the space 

 bounded by these five tubercles and each lateral keel, there is a shal- 

 lowly concave and rather broad depression of the carapace. In front 

 of these five tubercles, again, there are four others and still larger ones 

 (the two anterior ones apparentlj' of considerable size), arranged some- 

 what in the form of a .si|uare, any of whose sides would be greater 

 than the base of the isosceles triangle indicated by the other five. 



The upper surface of each of the abdominal segments bears a 

 tubercle in the centre, on its anterior edge, and another one on the 

 margin of each of the sides. The most prominent characteristic of the 

 species, in fact, is the possession of three widely distant, longitudinal 

 and tuberculated keels, which extend over nearly the whole length of 

 the uppjer surface of the body. 



To the right of the carapace, in front, there are indications of what 

 appears to have been a large pinching claw, and, if the appearances 

 presented are correctly interpreted, the sides of the fixed ramus of that 

 claw are also coarsely tuberculated. 



Until its exact generic position shall have been settled by the col- 

 lection of more perfect specimens, it may be convenient to designate 

 the present species as Hoploparia (?) Canadensis, though it is by no 

 means certain that it belongs to McCoy's genus of that name." 



Judging by the invertebrate fossils alone, it would seem probable 

 that the friable and fissile shales at Mill Creek which hold typical 

 example of Inoceramus problematicus may represent the " Niobrara 



