THE MICROSAURIAN FAMILY UROCORDYLID^E. 121 



posteriorly, where the acumination is inclosed by the parietal and postfrontal. The 

 parietals are by far the largest elements in the cranium. They form together an 

 oval which is elongate in the longitudinal diameter of the skull. They inclose 

 between them, in the median suture, the small pineal foramen. They are acu- 

 minate in front, with a broad truncate posterior base, where they are bounded by the 

 postparietals. The postparietal is nearly square, being somewhat wider than long. 

 It joins the tabulare and the parietal. The tabulare is elongate in the long diame- 

 ter of the skull. It ends anteriorly in a point which is inserted between the post- 

 orbital and the parietal, and bears a short protuberance posteriorly, much as does 

 the same element in the type species. 



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 prefrontal lies anterior to the orbit, of which it forms the ante- 

 rior border. The lacrimal has not been detected, although Jaekel (347) has indi- 

 cated 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 poste- 

 rior 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 squa- 

 mosal 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" ele- 

 ment. In closely allied species the "perisquamosal" is easily separated into its 

 component elements, and the morphology of the present skull would throw con- 

 siderable 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 cra- 

 nial 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. 



