1896.] Zoology. 145 



in the Testudinata has, however, yet to be produced, and I am entirely 

 willing to give up the view above defended, should it turn out on fur- 

 ther investigation to be untenable." 



There is no further investigation necessary. The bone in question 

 is a single element, as is shown, not only by comparative anatomy, but 

 also by embryology. This element always is free in the Testudines ; 

 it is free in the young Sphenodon ; and it is uniteJ with the exu.'cipi- 

 tal in the Squamata. There is not the slightest difficulty in this ques- 



One word about the squamosal. The squamosal of the Lacertilia 

 and Ophidia is connected with the parietals and stands on the quad- 

 rate, outside of this element we have in the Lacertilia with well devel- 

 oped postorbital arch another element, which originally is united with 

 the postorbital and is also connected with the squamosal and quadrate. 

 This bone is the prosquamosal] In Sphenodon the squamosal and pro- 

 squamosal are united, but in the Jurassic Saphseosaurus (Sauranodon) 

 these two elements are free as in the Lacertilia. In the Testudines the 

 squamosal represents the squamosal of Sphenodon, i. e., the squamosal 

 -f- prosquamosal of Saphseosaurus and the Lacertilia. Prof. Cope says : 

 u the squamosal of the Squamata is homologous to the paroccipital 

 (opisthotic, Huxley, occipital externe, Cuvier) of the Testudines. 

 This is impossible, since the paroccipital of the Testudines is the 

 homologue of the paroccipital process of the Lacertilia, which in front 

 contains, exactly as in the Testudines, the posterior semicircular canals. 

 In the Mosasauridffi we have the same conditions as in the generalized 

 Lacertilia. The paroccipital and exoccipital are united; connected 

 with the quadrate we find two elements— the inner one connected by 

 its upper branch with the parietal process ; the outer one with the 

 postorbital. These bones are, of course, homologous to the squamosal 

 and prosquamosal of the Lacertilia. 



II. The Affinities of the Mosasauridce.— Cope maintains, contrary to 

 my statement, " that in all Lacertilia the exoccipital supports the 

 quadrate, and that in the Pythonomorpha and the Ophidia the exoc- 

 cipital does not support it or generally touch it." He also maintains 

 " that the paroccipital (squamosal, Baur) does support the quadrate in 

 the Ophidia, while it is only in contact with a very small part of it in 

 the Lacertilia." I have denied in my last note that in all the Lacer- 

 tilia the exoccipital supports the quadrate, and I repeat it here. 



I have before me disarticulated and complete skulls of Iguana, 

 Ctenosaura, Amblyrhynchus and Conolophus. In none of these I find 

 an articular facet on the paroccipital (exoccipital Cope), for the 



