50 PATAGONIAN EXPEDITIONS: PALEONTOLOGY. 



junction of the squamosal and occipital. The basioccipital is long and 

 broad, with median convexity, which bears a ventral keel, and shallow 

 concavities on the sides. On each side of the basioccipital is a very large 

 vacuity, which was partly closed by the missing tympanic. The basi- 

 sphenoid is long, broad behind, tapering forward, so that the anterior end 

 is very narrow. The posterior nares extend farther forward than in L. 

 floweri, to the middle of m-. 



One of the most striking differences of this species from L. floweri is 

 the comparative shallowness, dorso-ventrally, of the facial region, even 

 making all due allowance for the vertical crushing which the skull has 

 undergone. In fact, this proportion approximates that found in Proter- 

 otherimn. The supra-orbital foramen, which is single on each side, is 

 very large. 



The horizontal ramus of the mandible is thick and stout, but shallower 

 dorso-ventrally than in L. floweri, thus making still more marked the dif- 

 ference between the two species in the vertical diameter of the skull. 



Measurements. 



Cranium, length to anterior rim of Face, depth at m-^ . . . ?.056 



orbit .126 Mandible, depth at mg . . . .029 



Occiput, width at base . . . .054 " " " P:f • • • -022 



The femur is very similar to that of Diadiaphorus ; the head is small, 

 sessile and deeply notched on the inner side by the triangular sulcus for 

 the round ligament. The great trochanter is very prominent and, though 

 not rising so high above the head as in DiadiapJwrus, is broader and 

 more recurved on the posterior side : the other trochanters are broken 

 away. The shaft, which has a very decided sigmoid curvature, is much 

 compressed laterally, thick antero-posteriorly ; the pit for the plantaris 

 muscle is very deep and conspicuous. 



The tibia is somewhat shorter than the femur and quite stout ; the 

 cnemial process, though very prominent and with massive proximal end, 

 is shorter than in Proterotherium, dying away more abruptly upon the 

 shaft. Of the distal end, the width slightly exceeds the thickness ; the 

 astragalar facets are not deeply concave, despite the prominence of the 

 intercondylar ridge, the dorsal tongue of which is somewhat better defined 

 than in Proterotherium. Except near the dorsal side, to which the very 

 low internal malleolus is confined, the astragalar facet has no raised inner 

 margin. 



