566 F. B. Loomis — New Mosasaur from the Ft. Pierre. 



not greatly differentiated though the first is slightly larger 

 than the others. The phalanges are those typical of the genus. 

 We have two paddles to judge from, and they would seem to 

 indicate that the formula was 4 6 6 6 4. This allows for one 

 lacking on the first digit in my drawing, and for three lacking 

 on the fourth and fifth digits. 



The hind limb material is not as abundant or perfect as the 

 front limb. I have no ilium or ischium. A femur, which 

 must belong to this form as no other mosasaurs were found 

 here, is a large flattened bone, expanded both proximally and 

 distally. The articular ends, however, are only moderately 

 thickened. The tibia is considerably the larger bone of the 



Fig. 9. 



Fig. 9. The hind limb showing the femur, tibia, fibula, tarsals, and four 

 metatarsals. 1/6 nat. size. 



two in the fore leg. It has the ends much thickened and 

 expanded. The fibula differs from what would be expected, 

 being very short, the ends thick and expanded, the inner bor- 

 der concave, and the outer convex and much thinned. 



In the tarsus three bones were ossified, two larger and one 

 tiny. This again is more ossification than is characteristic of 

 Platecarpus. Four metatarsals were found with this speci- 

 men, all of generally uniform size, except that the fifth is 

 expanded proximally as is typical. 



Throughout the preceding description the figures are care- 

 fully drawn to scale, so that relatively few measurements have 

 been given. I think it entirely safe to take others from the 

 figures. 



Amherst College. 



