WILLISTON AND MOODIE : OGMODIRUS MARTINII. 69 



emigration of the osteoblastic tissue from the medullary canal, 

 which in this species is highly developed. The mounds correspond 

 to the points of entrance of the Canalis ossificans perforans, which 

 in mammals transmit the osteoblasts from the medullary portion 

 of the diaphysis into the epiphysis. The element is regarded as a 

 humerus simply on account of its shortness, since it has hereto- 

 fore been an invariable rule among the plesiosaurs that the shorter 

 propodial is the humerus. 



The humerus is remarkably short and broad, thickened at the 

 proximal end, so that at this point it shows a rounded outline in 

 cross section. The element gradually expands distally, especially 

 toward the median plane, so that finally the distal end appears 

 partly separated by an indentation. On the upper surface the 

 bone has been distinctly marked on the radial edge (plate III, 

 fig. 1) by the teeth of some predaceous fish or reptile, inflicted 

 shortly after the death of the animal. This is not a rare occurrence 

 among Kansas Cretaceous fossils, and indicates that some of the 

 Cretaceous vertebrates were carrion feeders. 



There are no well-developed facettes on the ends of the hu- 

 merus such as is so common among other plesiosaurian species. 



Measurements of Humerus. 



Length 0.152 m. 



Width at proximal end 0.070 m. 



Width at middle 0.071 m. 



Width at distal end 0.112 m. 



Thickness at proximal end 0.050 m. 



Thickness at distal end 0.036 m. 



The radius and ulna are flattened, rounded plates, with broad 

 peripheral surfaces for articular cartilage. The ulna is much 

 smaller than the radius and is more nearly rounded. The radius 

 is elongate transversely, with the ventral surface concave and 

 marked by several vascular pits. (Plate II.) 



MeasuremenUi of Ulna. 



Greatest breadth 47 mm. 



Least breadth 42 mm. 



Greatest thickness 21 mm. 



Measurements of Radius. 



Greatest breadth 70 mm. 



Least breadth 52 mm. 



Greatest thickness 25 mm. 



The car pals (plate II) are of the same character as the radius 

 and ulna. They can only be distinguished by size. The largest 



