306 BULLETIN UNITED STATES GEOLOGICAL SUEVEY. 



parieto quadrate arches ; that all arches are absent from the Amphis- 

 baenian and Typhlophthalm suborders, and the zygomatic arch is in- 

 complete in the Varanidce. So this character has no ordinal signifi- 

 cance. 



Fourth. — Professor Owen opposes my statement that " there is no 

 ^uadratojugal arch" by the observation that "in no reptile does the 

 jugal or malar bone join the quadrate or tympanic bone". Professor 

 Owen has here again fallen into error, since, in Hatteria (Sphenodon) 

 and the order Ehi/nchocephalia, the malar does, according to Giinther, 

 articulate directly with the quadrate.* I cannot now refer to Professor 

 Owen's early description of the same genus to see whether he has 

 himself not pointed out this structure before Dr. Giinther. Professor 

 Owen knows also that the malar is connected with the quadrate in the 

 €rocodilia by the mediation of a short quadrato-jugal bone, which fact 

 is not directly contradicted in the sentence above quoted from his article. 

 My object in citing this character was to show the distinction between 

 the Fytlionomorplm and the orders named. 



Fifths as to the form of the quadrate bone. — Like myself, Professor 

 Owen finds it to differ from the corresponding elements in other orders. 

 I have, however, not cited it in evidence of Ophidian aftiuity, although 

 there is no propriety in Professor Owen's remark (p. 693) that " the 

 tympanic (quadrate) bone alone suffices to refute the Ophidian hypothe- 

 sis of the Mosasauroids". Comparing it with the quadrate of specialized 

 snakes, he naturally finds differences; but he will find near resemblances 

 if he will examine the same element in the Tortricine and the other low or 

 generalized snakes which MtiUer combined under the name of Microsto- 

 mata.f Besides, great variations in the proportions of this and of various 

 other elements are not inconsistent with coordinal affinity. 



Sixth, as to the distinctness or coalescence of the nasal bones icith surround' 

 ing parts. — Although this point is of no importance to the main ques- 

 tion, I here observe that most of my specimens differ from the one 

 figured and described by Professor Owen (fig. 14). He states that m. 

 the Mosasaurus missuriensis and Liodon anceps, the nasal bones are dis- 

 tinct ; in various species of CUdastes and Platecarpus, they are coossified 

 with other elements. 



Seventh, as to the bony palate. — The partially free and dentigerous 

 pterygoid bone is Ophidian as well as Lacertilian, but is not identical 

 with the structure in the snakes, as I have pointed out. The supposed 

 contact of these bones on the median line noted in Mosasaurus mis- 

 suriensis is probably due to distortion, as it does not exist in most of the 

 Pylhonomorphous skulls which I have seen. 



F'ighth, as to the mandibular hinge. — I have not cited this in evidence 

 of any special affinity, for Pythonoinorpha might be without it, and not 

 lose their ordinal place. But there is a much greater resemblance be- 



* Ou the Anatomy of Hatteria, in Trans. Koyal Society, 1867, pi. i. 



tSee my fig. of cranium of Cylindrophis, Proc. Am. Ass. Adv. Sci. six. p. 217. 



