65 



out crossing, however), gradually disappear posteriorly. 

 These various ridges form four deep concavities on the 

 upper surface of the skull: (i) The largest already men- 

 tioned, between the parietals and the posterior part of the 

 frontals ; (2) that marked by the suture between the nasals 

 and frontal, not so large; (3 and 4) two much smaller 

 lateral ridges between the sagittal and superciliar}^ ridges. 

 This great irregularity of the upper surface of the head is, so 

 far as is yet known, peculiar to Uintathcriiiin. 



Parietals. — The peculiar feature of these bones is the huge 

 pair of projections (the so-called "posterior horn cores") to 

 which they give rise. The <juter margin of these processes 

 is nearly straight ; the inner margin for its upper two thirds 

 is also straight, the lower third curving in a high strong ridge 

 to meet its fellow. The anterior face is rounded and pro- 

 duced into the long crest of the Irontals, while the posterior 

 face is flattened and produced into a similar but shorter and 

 higher crest which joins the supra-occipital. At the base of 

 these processes their greatest diameter is fore and aft, while 

 at the top it is transverse. They project upwards and out- 

 wards, but are not curved as in Dinoceras, nor are their 

 upper borders so much arched. Their greatest diameter at 

 top is at right angles to the corresponding measurement in 

 this last-named genus. Behind the ridge which connects 

 these projections, the parietals curve sharply upward to a 

 high occipital crest; between which and the projections they 

 form a deep basin whose floor is raised above that formed by 

 the frontals immediately anterior to it. This arrangement 

 differs from that of both Loxo/ophodon and Dinoceras, espe- 

 cially from the latter. The tempoi'al fossae are of great 

 length, deeply concave, but rather low from above down- 

 wards, formed almost entirely by the parietals, and bounded 

 posteriorly by a sharp outward curve of these bones. They 

 are of about the same proportionate length, but higher and 

 very much deeper tiian in Loxo/ophodon ; and are not nearly 

 so long as in Dinoceras, in which genus the parietals expand 

 far behind the horn-like processes. In our specimen the pos- 

 terior part of the fossa is pierced by numerous small venous 

 foramina, and corresponds precisely in every way, save that 



