150 Field Columbian Museum — Geology, Vol. II. 



uniting them in a complete basin, with the necessary curvatures, it 

 transpires that the opening of the pelvis had a diameter of about seven- 

 eighths of an inch, while the outlet could have measured but a trifle more 

 than half an inch. 



Femur. PI. XLIII, Figs. 4, 5. Both femora are preserved, separated 

 by a short distance from the pelvis. The neck is directed upward and at 

 a slight angle inward; it is cylindrical, the head only a little dilated and 

 with its convexity only a little oblique to the axis of the bone; that is, the 

 plane of the rim is nearly, but not quite, rectangular to the axis of the 

 shaft. The trochanter stands a little to the outer side of the middle axis 

 of the bone. From its upper angle a ridged process runs backward for a 

 short distance, to the inner side of which, a little below the free, upper 

 concave margin of bone, there is a small pneumatic opening. On the 

 outer side, the margin of the shaft is convex for a short distance, and is 

 then concave throughout to the extremity. On the inner side above, the 

 margin is correspondingly concave; below this to the condyle it is con- 

 vex. The upper part of the bone was evidently, in life, nearly cylindrical; 

 below it seems to have been wider and somewhat flattened. Near the 

 middle behind, beginning a little above the condylar surface, there is a 

 narrow, elongated, longitudinal ridge for the attachment of a muscle. 

 The distal articular surface cannot be clearly made out in the crushed 

 specimens. The bone had in life, apparently, a marked anterior curva- 

 ture, as in Pteranodon. 



MEASUREMENTS OF FEMUR. 



mm. 



Length 81 



Diameter of neck 6 



Diameter of shaft, upper third 7 



Diameter through condyles as crushed , 13 



Femur of Pteranodon ingens Marsh, PI. XLIII, Figs. 1-3. The con- 

 vexity of the head is regular, covering nearly half of a circle transversely, 

 probably a little less in the conjugate diameter, the surface thus forming 

 an oval or ovate figure, the plane of whose base is nearly at right angles 

 to the long diameter of the bone. The convex surface is sharply limited 

 from the neck. The neck is cylindrical, rather stout, and is directed 

 nearly vertically downward. The rounded and moderately prominent 

 trochanter is placed over the middle of the shaft, descending into the 

 concavity at the side of the neck, and externally separated from the 

 margin of the bone. The shaft is nearly of equal width throughout; 

 doubtless in life it was nearly cylindrical, with a strong anterior curvature, 

 and a flattening in the popliteal region. The sharp margin of the inner 

 condvle encompasses nearly half a circle. The outer condyle, though 



