There are four elements which take part in the formation of the posterior border of the skull. These are the postparietal, the tabulare, the squamosal, and the supratemporal. It is very unusual for the supratemporal to reach the posterior edge of the cranium. The pref rental lies anterior to the orbit, of which it forms the anterior border. The lacrimal has not been detected, although Jaekel (347) has indicated it in his drawings of the skull of the type species. The maxilla is elongate and forms the lateral border of the skull. No teeth have been detected, although they were doubtless the same as Jaekel has figured in _D. punctolineatus_. The jugal is an elongate element joining the maxilla posteriorly. Jaekel included this element in his "perisquamosal," but the sutures are clearly evident in the present specimen and there is no evidence of a structure at all similar to a "perisquamosal." The postorbital is fully as large as the jugal which it joins, forming a part of the posterior border of the orbit and ending posteriorly in a point which is inclosed by the tabulare and the squamosal. The postfrontal with the foregoing element forms the entire posterior border of the orbit and it likewise ends in a point inclosed by the parietal and the postorbital. The quadratojugal has much the same shape and relations as in _D. punctolineatus_, although it is located further back. The squamosal is also elongate, as are most of the posterior cranial elements, and it also has an acumination which is directed forward and is inclosed by the postorbital and jugal. The anterior suture of this element is rather indistinct, but it is, I believe, as represented (fig. 24). The element is elongate and is prolonged posteriorly to form the horn, which ends in a blunt point and is not sharp, as in the type species. Jaekel (347) regards the species _Diceratosaurus punctolineatus_ Cope as being unparalleled among known vertebrates in the possession of a "perisquamosal" element. In closely allied species the "perisquamosal" is easily separated into its component elements, and the morphology of the present skull would throw considerable doubt on Jaekel's interpretation of the skull of the type species. Another specimen, described below as another species of this genus, shows no evidence of this fusion. So far as I can learn, there have been no cases of true fusion of cranial elements correctly reported, unless it be that which possibly exists between the two frontals in the skull of _Diplocaulus_. It was on the basis of such fusions that Maggi (397) proposed to derive the interparietals of the primates from the tabulare of the stegocephalians. The posterior outline of the skull in the present specimen is not well preserved and the outline as given may be slightly inaccurate. The indentation figured by Jaekel in the posterior border of the skull of the type form is not present in the species under discussion.