540 S. W. WILLISTON 



Plalecarpus. Quite certain it is that in the specimens under consider- 

 ation there are no such separate bones. Incidentally I may mention 

 that in Pteranodon among pterodactyls the fibula is supposed to be 

 absolutely wanting, yet in a specimen in our collection I find distinct 

 remains of it fused with the tibia. 



I have for some time agreed with Thyng and v. Huene in their 

 conclusion that the real squamosal bone of the mosasaurs (and 

 lizards) is that connecting the post-orbital with the so-called supra- 

 temporal bone, though Thyng, not reading my text but examining my 

 figure alone, goes to considerable trouble to prove that I was wrong 

 (see Biological Bulletin, VII, 189 ff.). But I agree with neither of 

 these authors in considering the posterior element, that intercalated 

 between the squamosal and exoccipital and pro-otic, as the so-called 

 supratemporal. It is a matter of surprise to me how persistently 

 all students of the temporal arch of the mosasaurs and lizards have 

 ignored the description and figures of this bone given by Cope and 

 myself. From Baur to the present time, save Merriam and my- 

 self, no one has paid any heed to Cope's descriptions. At the risk 

 of being discursive I will quote what I have previously published in 

 the article already quoted: 



Baur vigorously urged that the bone at the end of the suspensorium is the 

 squamosal, but Baur never fully understood the relations of this bone in the mosa- 

 saurs, as is evidenced by his faulty description of it.^ As Cope has repeatedly 

 affirmed and as I have confirmed,^ this so-called squamosal (supratemporal 

 Huene) of the mosasaurs is intercalated between the exoccipital and the pro-otic, 

 extending far inward, nearly to the surface of the braincase. It needs but a 

 moment's consideration by any one familiar with the relations of this bone in these 

 animals and in the mammals to be convinced that such remarkably different con- 

 ditions cannot be those of the same bone. The inner part of the (squamosal) 

 [deeply wedged in as it is between two cartilage bones] corresponds quite well with 

 the outer part of the opisthotic, which was not found in the lizard embryo 

 by Parker. "In some of the genera of Stegocephala the paroccipital is free from 

 the exoccipital; in others {Mas.todonsaurus) it is co-ossified with the exoccipital. 

 The paroccipital is in relation to a dermal plate which is very improperly called 

 the epiotic. I propose the name paroccipital plate for it."3 



1 Journal of Morphology (1892), VII, 14. 



2 Cope, Trans. Amer. Phil. Soc. (1892), XVII, 19; Williston, Univ. Geol. Survey 

 (1898), IV, 121. 



3 Baur, Journal oj Morphology (1889), III, 469. 



