G. R. Wieland — -Upper Cretaceous Turtles. 131 



{f) The humerus of specimen 778 has much more rugose 

 radial and ulnar crests than that of Osteopygis. Also corre- 

 sponding well with the presence of pleuro-marginal fontanelles, 

 the distal end is well rounded like that of Chelydra. The 

 general form is chelic to chelicoid. The angle between the 

 proximal crests is much more obtuse than in any of the Chely- 

 dridse, and the ectepicondylar foramen is well enclosed. This 

 latter is a retained primitive position. 



The Pelvis. — The pelvis of the type just described is for- 

 tunately present as mentioned above, and can only be given 

 separate description, since this portion of the skeleton of 

 Osteopygis and allied forms has not hitherto been known. 

 Although the median symphysial borders of both the pubes 

 and ischia are broken away, the remainder of the pelvic out- 

 line is quite entire, and has warranted the restoration shown 

 in Plate IX. There the parts are shown laid out flatwise and 

 as seen from their lower, that is, from the acetabular side. 

 The general structure and outline of parts is much like that 

 seen in Chelydra, except that the distal articular surface of 

 the pubis is much longer as in the marine turtle Toxochelys, 

 which also has a somewhat Chelydra-like pelvis. 



It is to be noted, that the preceding facts and comparisons 

 indicate a turtle close to Propleura (Osteopygis) erosa Cope, 

 the type of which has not been figured. Cope says the species 

 0. erosus has vertebral bones more than twice as long as wide, 

 which is not the case in the 1st and 2d vertebrals, the only 

 ones preserved, in the turtle before us. Completer knowledge 

 of the two species may, however, show their identity. From 

 Propleura (Osteopygis) sopita separation is based on the dif- 

 ferent proportions of the marginals, though in most other 

 respects there is close agreement so far as may be adjudged 

 from the fragmentary type material described and figured.* 

 But generic separation of these specimens from Osteopygis 

 must hold as based on the presence of well-marked lateral 

 pleuro-marginal fontanelles, conical rib pits of the marginals, 

 and humeri with smooth not sculptured distal ends. 



Measurements of Propleura borealis. 



Greatest width of Carapace . ,. 65*6 



Length of Marginals measured along the outer edge: 



1st Marginal 10*0 



2d " _ 9-5 



3d " _ 7-5 



4th " _ 



5th " _ 9-0 



6th " .._ 10*4 



7th " : 11*0 



* Extinct Batrachia, Reptilia and Aves, Plate VII. 



cm 



