310 BULLETIN UNITED STATES GEOLOGICAL SURVEY. 



Pythonomorpha are nearer to the Ophidia than are the Lacertilia to estab- 

 lish the truth of my position. Five of the seven characters enumerated 

 above are so clearly of this nature that my statement is abundantly justi- 

 fied. And it may be true without necessarily implying close affinity with 

 the typical serpents. Of course, the points of approximation in Ophidia 

 are to those which do not present the extreme of modification of the order, 

 but to such more generalized forms as the Tortrioidce, Urycidce, ScolecopM- 

 dia, etc., which are also nearest the lizards. Had Professor Owen desired 

 a character in addition to the numerous ones which I have cited, in which 

 they do not resemble the Ophidia, he might have added the absence of 

 the trabecular grooves of the basi- and prespheuoid, noticed by Huxley 

 as distinguishing the serpents from the Lacertilia. But this interesting 

 feature does not characterize the order Ophidia. The groove is reduced 

 in Xenopeltis, and is wanting in the TypMopidce. 



It only remains to show the inexact nature of the comparison which 

 Professor Owen draws between the relations of the seals to other Car- 

 nivora, and those existing between the Pythonomorpha and Lacertilia. 

 These relations he considers to be similar ; that is, that as the sefils are 

 an aquatic form of Garnivora, so the Pythonomorpha are an aquatic form 

 of Lacertilia. I affirm, in opposition to this view, that the relations in 

 the two cases are totally distinct. 



The seals agree with the Garnivora in all those important respects in 

 which I have shown the Pythonomorpha to differ from the lizards. The 

 seals possess a sternum and sacrum like other Garnivora; neither do 

 they differ in the structure of the brain-case nor otic region from the 

 same order. The teeth have dentinal roots like other Garnivora; and 

 although the limbs are adapted for aquatic use, and formed superficially 

 like those of Pythonomorpha, their bones are like those of Garnivora in 

 all important respects. They possess the usual condylar articular faces, 

 even to the phalanges; they have ungues also ; so that all the parts 

 common to the limbs of Garnivora may be found in the seals. The dif- 

 ference between the limbs of Lacertilia and Pythonomorpha is radical in 

 general and in particular. 



, Professor Owen objects to the name which I have given to the order, 

 and seems to think it conveys an erroneous impression. Such an im- 

 pression as to my meaning appears to have been made upon my critic : 

 what I mean to convey by it can be readily understood by reference to 

 my definitions. The name would not be erroneous even if applied to an 

 eel or other serpent like animal without the least affinity to Ophidia, and 

 is rather more appropriate than the names Ichthyopterygia for reptiles 

 whose fins are not truly like those of fishes, or Dinosauria, some of 

 which are small and weak. As to the use of the term sea-serpent, since 

 I have not referred these reptiles to the Ophidia, the term involves no 

 error. I have used the same expression in writing of the contemporary 

 Masmosaurij of totally distinct affinities. As the first name proposed 

 for these reptiles as a natural group, with a definition, the name I have 

 given will stand in accordance with nil the rnlea of noraenclature. 



