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UINTA SELENODONTS 



somewhat above the general level of the forehead, and in 

 L. gracilis is placed quite far forward, the anterior border being above the line 

 between m 1 - and m', while in L. marshi this border is above the hinder half 

 of m^-. Despite the long, decurved postorbital process of the frontal the orbit 

 is quite widely open behind. 



In the skulls which I have had the opportunity of examining, most of 

 the sutures are obliterated, so that it is difficult and often impossible to 

 make out the limits of the individual bones. The occiput is rather low and 

 is bounded by a prominent crest ; the condyles are large and extend conspicu- 

 ously behind the plane of the occiput, and the paroccipital processes also are 

 curved strongly backward. The coronal suture is not visible in any of the 

 specimens, but assuming that it occupied the same position as in Protylopus, 

 then, as in that genus, the temporal ridges must extend for some distance 

 over upon the parietals, but for a shorter distance and converging more 

 rapidly to the sagittal crest than in the latter. The sagittal crest is short, 

 as is the whole postorbital part of the cranium. The parietals are broad and 

 gently arched and are suddenly and deeply constricted at the postorbital notch, 

 which follows immediately behind the orbits. Above the orbits the frontals 

 are broad and slightly concave, but they narrow rapidly towards the front 

 end. The postorbital process is very long and prominent, much more so 

 than in Protylopus, but this length is partly due to the great depth of the 

 postorbital constriction ; the process is broad and heavy and bent downward, 

 so as to form a partial hinder boundary to the orbit, though the enclosure is 

 very far from complete. The supraorbital foramina are shifted much nearer to 

 the median line than in Protylopus, and broad, well-defined grooves lead for- 

 ward from them. No supraorbital notch is present. The nasals are long 

 narrow, and slender, and are slightly convex both transversely and longitu- 

 dinally, but they are truncated in front and cease at the line of p x . In con- 

 sequence of this the anterior nares, though rather small, are much more 

 steeply inclined than in Protylopus, and their oblique position suggests that 

 here we find the beginnings of the transformation which led to such remark- 

 able results in Protoceras. The premaxillaries have quite stout, though 

 depressed, horizontal rami, in which the incisors are inserted ; the ascend- 

 ing rami, on the contrary, are very narrow, much more so than in Protylo- 

 pus, and seem not to reach the nasals, though this is difficult to determine 

 positively. 



The maxillary is quite extraordinarily elongate, and forms much the 



