12 



University of California Publications. 



[Geolooy 



tarsus than would be found in the average of the species. Com- 

 pared with this Recent specimen, the type of Sarcorhamphus 

 clarki shows many of the same points of difference that are 

 brought out in comparison with Gymnogyps, i. e., slenderness of 

 the shaft and its nearly uniform width throughout most of its 

 length ; by its high intercotylar tuberosity and the narrow par- 

 tition separating the two proximal foramina. 



The two bones are almost identical in length, which makes comparison 

 easier. The view of the two specimens from the anterior side shows the 

 fossil form to differ in the following details: The inner tibial facet is 

 raised farther above the outer one, the intervening tuberosity is larger 

 and more globular. The diameter of the shaft contracts more suddenly 

 just below the head. The excavation of the shaft in the head region is 

 more abrupt and more restricted. The partition separating the two 

 proximal foramina is not more than two-thirds as wide. The attachment 

 of the tibialis anticus blocks the whole anterior furrow which is continued 

 down the shaft on a shallower level to disappear entirely before reaching 

 the middle point of the shaft. The narrowest point of the shaft is 

 at or above the middle point instead of below it. The actual width of 

 the shaft is markedly less. The foot is narrower, the trochleae are longer 

 but more slender. 



Seen from the outside, the tuberosity appears more knob-shaped. The 

 hypotarsus is placed higher and its outer ridge is less pronounced. The 

 lateral margin of the outer articular facet drops downward and forward 

 more abruptly. The shaft from this aspect is appreciably thicker 

 throughout its length. The outer trochlea appears less stubby. 



From the posterior and internal aspects no important differences are 

 noticeable other than have been recorded above. 



When viewed from the tibial end, the greater anteroposterior 

 diameter of the head is noticeable. The inner articular facet is larger 

 and its greatest diameter lies in a plane more nearly parallel to the 

 sagittal plane. The triangular space posterior to the tuberosity is nearly 

 equilateral and not longer on its anteroexternal face. The groove 

 separating the hypotarsus from the head is shallower and less perfectly 

 defined, especially at its external end. The posterior profile of the 

 h3 r potarsus is much less deeply indented. 



The specimen was also compared with Gymnogyps calif or- 

 nianus Recent specimen. The fossil form is distinguishable by 

 much the same characters as were noticed in its comparison 

 with Sarcorhamphus gryphus. The total length of the bone 

 is ten millimeters greater and the breadth at either end exceeds 

 that of Gymnogyps, yet the shaft is markedly narrower at all 

 corresponding points throughout its length. The lateral toes 



