WILLISTON AND MOODIE : OGMODIRUS MARTINII. 71 



Measurements of the Ilium. 



Length 0.148 m. 



Width at proximal end ' 0.018 m. 



Width at distal end 0.054 m. 



Length of the sacral rib articular fossa 0.043 m. 



Width of the sacral rib articular fossa 0.028 m. 



The portion of the pubis (plate IV, fig. 4) consists of the articu- 

 lar portion. It is marked, as are the other elements of the skeleton, 

 by fine vascular pits and lines. The diameter of the articular end 

 is 0.037 m. 



Hind paddle. The left femur of the hind limb is preserved. It 

 is distinguished from the humerus by its slender, nearly straight 

 form (plate IV, fig. 1) and its almost circular cross-section at the 

 proximal end. There are no sharply defined articular facettes. 

 On the superior surface there is a roughened process for strong 

 muscular attachment. Its position is such that this process can 

 be regarded in a certain sense as a trochanter. 



On the radial surface of the femur there is a distinct rounded 

 foramen, similar to those described by the writers elsewhere. 

 Since the bone is broken at the plane of this foramen, it shows 

 that the foramen is the opening of an elongate rounded canal, 

 which in turn leads into a large medullary cavity which sends 

 spicular spaces into the surrounding bone. (Plate III, fig. 3.) 

 This condition has been commented on several times, but no ex- 

 planation has been offered to explain it. The structure has all of 

 the appearance of the so-called "periosteal buds" so commonly 

 figured in textbooks of microscopic anatomy. 



Measurements of the Femur. 



Length 0.175 m. 



Diameter of the lateral foramen 0.006 m. 



Diameter of the medullary cavity 0.015 m. 



Length of the canal 0.020 m. 



Length of the medullary cavity 0.025 m. 



Length of one of the smaller canals 0.001 m. 



In view of the possibility of identity, or at least a close relation- 

 ship, between Ogmodirus and Embaphias circulosus Cope, we give 

 herewith figures of the best of the type specimen of this genus 

 and species (plate V) as it is now preserved in the Academy of Nat- 

 ural Sciences of Philadelphia. The type, collected by Mr. F. H. 

 Charles from the Great Bend of the Missouri river. South Dakota, 

 in 1893, consists of two dorsal and one cervical vertebra. The 

 specimens present no generic characters and can not be again 



