OSTEOLOGY OF AMERICAN PERMIAN VERTEBRATES 371 



and tabulare, is slender throughout, slightly dilated at its extremity, 

 and is directed outward and backward at an angle of about 45 

 degrees with the long axis of the skull; it is gently curved down- 

 ward at its extremity to articulate with the squamosal, quadrate, 

 and paroccipital. There can be no doubt of the separation of the 

 element forming the chief part of the arch; I identify it as the 

 tabulare. I think that my reasons for so doing are valid. The 

 tabulare in the early reptiles and amphibians is always associated 

 with the outer end of the paroccipital. The only other element 

 that could possibly be in this position is the so-called supratemporal 

 or suprasquamosal. That the present bone is the supratemporal 

 of contemporary authors is, I think, very improbable. This bone 

 is never known to be in relation with the paroccipital and quadrate, 

 relations that the tabulare invariably has; it always articulates 

 with the postfrontal or postorbital when present. I think that 

 doubt of its identity may be dismissed here; it is indisputably the 

 tabulare or "epiotic." 



It is now nearly ten years since I wrote the following: 

 I prefer to call the bone articulating with the postorbital [in the lizards] 

 the squamosal, the bone which in other reptiles articulates with the post- 

 orbital behind. Of course if this is the real squamosal, the posterior element 

 cannot be the squamosal. ■. . . . The inner part of the so-caUed squamosal 

 in the mosasaurs [the posterior bone of the arch] corresponds quite well with the 

 outer part of the paroccipital or opisthotic element, which was not found by 

 Parker in the lizard embryo. Referring now to the figures it will be seen that 

 the outer part corresponds fairly well with the bone called the "epiotic." 

 .... It may be objected that the presence of an epiotic bone [tabulare] in 

 the lizards is a far too primitive character, but we are now quite certain that 

 the lizards are an exceedingly old group, probably dating from the Permian, 

 and that they have not a few primitive characters,"'' etc. 



The condition of this bone in the mosasaurs is such that one 

 might easily conceive that it is a compound bone formed by the 

 outer part of the paroccipital and the tabulare fused together, 

 though I no longer beheve that any part of it is the paroccipital. 

 It was Cope who insisted that the bone in the mosasaurs is the 

 paroccipital only, a view that was vigorously combated by Baur. 

 This view, that the bone is the tabulare, I have consistently held 



'■ Williston, Biol. Bull. (1904), p. 190. 



