NO. I.] THE SKULL IN THE MOSASAURID^. 19 



Zoological Society of London, in which the view expressed by 



"^M:."n1er considers the Mosasaurs a sub-order o,..e 

 Sauamata and can see no reason for not regarding the Creta- 

 cels Doiichosauria as the progenitors of the Mosasa- ^^^^^^^ 

 the same time of '<the true Lacertiha, of which the Pleistocene 

 and recent VaranidcB are a family." u- ui„ 



In re'ard to my opinion that the Mosasaurs represent highly 

 speiSed aquatic forms, he asks : " Does this mean that hmbs 

 stngiy s'peciai..ed as those of the Monitors can have been 

 modified into the paddles of the Mosasaurs ? A glance at 

 fiiTiires suffices to refute such a theory. . t ., 



^The three sub-orders, Dolichosauria, Pythonomorpha, Lacer- 

 tilia are thus characterized : — ^ .^. 



:i Dolichosauria, .5-./ cervical vertebrae. Extremities ar- 

 chaic i c approaching the Batrachian type. 



T{1 Pylnomcfka, 9 or ,0 cervical vertebrae. Extremtt.es 

 paddle-shaped, with hyperphalangy 



..III Laccrtilia, 8 or 9 cervical vertebrae. Fibula reduced 

 proximally ; fifth metatarsal reduced in length and strongly mod- 



'" We may now first proceed to examine the Dolichosauria. 

 It has To be stated first that Boulenger believes that Kornhu_ 

 be 's >///</.«-'"„/.««.,«« belongs to the Do hchosauridae and 

 nossibly to the genus DoUchosaurus proper. I do not think it 

 is posJbe to determine at present whether Hydro.aurus Us. 

 LS belongs to the Dolichosaurida. or not ; one thing, how- 

 ever seems certain, that the number of cervicals was not 15-.7, 

 but Considerably less. But this is of little interest m this ques- 

 tron It only needs to be examined whether these animals rep 

 resent tenerllized forms or not. Mr. Boulenger speaks about 

 he arcfalc extremities approaching the Batrachian type, and 

 lives a cTpy of Kornhuber's figure of the hind limb, showing 



' ^cctrditlrf ornhuber there are four tarsal bones, which 

 /vccoraiu^ lw i elements m Varanus. 



he homologizes very properly with the tour eieme ^ 



Tn regard to the fifth metatarsal and the phalanges, he says^ 

 ' D r Metata^^^ der funften Zehe (-^^ 5) zeigt den U^^^^^ 



seine obere Flache, ist entsprechend dem Verhaltnisse bei re 



1 Kornhuber, Dr. A., Ue^er nnen neuen fossUen Saurur aus Lenna, Abhandl. 

 k. k. geol. Reichsanstalt Bd., V, Heft. 4. Wien, 1873- 



