COPE ON OWEN ON PYTHONOMOEPHA. 305 



Geological Survey of the Territories (p. 126) is stated as follows : — "As a 

 conclusion, it may be decided that these reptiles were not nearly related 

 to the Vara7iid(s, as has been supposed, but constitute a distinct order of 

 the Streptostylicate group ; that they are primarily related to the Im- 

 certilia, secondarily to the Ophidia, and thirdly to the Sauropterygia ^ 

 that they present more points of affinity to the serpents than does any 

 other order ; and that their nearest point of relationship in the Lacer- 

 tilia is the Varanidce or Thecaglossa.''^ 



Professor Owen admits that the Mosasaurs are not so nearly related 

 to the Varanidce as was once supposed, as he cannot do otherwise ; but 

 he will not allow that they represent a distinct order of reptiles, but en- 

 deavors to show that they are Lacertilia. He especially condemns the 

 conclusion that " they present more points of affinity to the Ophidia 

 than does any other order". In doing this, he passes in review many 

 of their characters, of which I notice sixteen, to which he attaches tbev 

 chief significance. I now propose to show that the results of Professor 

 Owen's newer examination are in accord with my own so far as they 

 have gone, but that he fails to observe several important points of 

 structure necessary to the question. But espec ally does he fail of juste 

 criticism, because he ascribes to me views which I do not hold, by fre- 

 quently pointing out the Lacertilian character of certain structures, frona 

 which it is to be inferred that I have regarded them as Ophidian, when 

 I have explicitly stated (Cretaceous Vertebrata, etc., p. 125) the reverse; 

 and he thus exaggerates the expression of Ophidian affinity which is 

 found in the concluding paragraph above quoted. 



First character. — Professor Owen declares that in the lateral descend- 

 ing processes of the basioccipital the FytJionomorpha display Lacertiliaus 

 affinity, since lizards possess them and serpents do not. I will only ob- 

 serve here that the same character would relate them to the Iclithyo- 

 pterygia and turtles ; and that if the median keel be evidence of ordinal 

 affinity, then serpents must be nearly allied to the alligator, for both 

 these reptiles possess it. But in reality the occipital segment in Pijtho- 

 nomorphain its superior parts is more like that of Ophidia than Lacertilia, 

 and the inferior form is not very different from that of the snakes also. 



Second, the connection between the exoccipital andprootic and the sub- 

 pensorium. — Professor Owen remarks (p. 687), — " Mosasaurus (fig. 5), 

 shows the Lacertian extension and connection of the ex- and paroccipi- 

 tals, with the expansion and abutment of the latter against the mastoid 

 and squamosal," etc. Here is a positive error of fact, which it is diffi- 

 cult to understand in view of the various descriptions and figures which 

 I have given of the parts. The " paroccipitals" (opisthotics) are not 

 connate with the exoccipitals, but are large and distinct. 



Third, the cranial arches. — These are wanting in Ophidia, but present 



in Pythonomorpha and many lizards; hence Professor Owen pronounces 



that these extinct forms are Lacertilia. He has forgotten that the 



large family of Gecconidce among the latter possess no zygomatic nor 



Bull. iv. No. 1—20 



