126 



3. The extensive freedom of the palatine is less complete than that 

 of the same element in the Ophidia, and much more so than in most Lacertilia, 

 resembling, in this respect, the Varanidce. 



4. The close articulation of the parietal with the supraoccipital is seen 

 in the serpents and the amphisbaenian section of the lizards, but not in true 

 lizards; while the supraoccipital crest is a character of serpents, not of lizards 

 or saurians. 



5. The presence of fronto-parietal fontanelle is very general in Lacertilia 

 and various extinct saurians, while it is unknown in serpents, crocodiles, and 

 other groups. 



6. The parieto-quadrate arch belongs to several groups of saurians and the 

 Lacertilia, but not to serpents. 



7. The squamosal bone has a similar distribution among reptilian orders. 



8. The firm attachment of the maxillary to the other bones has the same 

 significance. 



9. The want of sutural symphysis is seen in snakes, the varanian lizards, 

 Ichthyosaurus, &c. ; but not in Lacertilia generally,- Testudinata, Sauro- 

 plerygia, or Crocodilia. 



10. The simple premaxillary is general in the streptostylicate orders, and 

 uncommon in the others. 



11. The underarching of the olfactory lobes by frontal lamina? is char- 

 acteristic of some lizards (the Varan i) and of all snakes. 



The above characters are of very unequal value, and may, in many cases, 

 be departed from by forms hereafter discovered without invalidating their 

 ordinal relations with the Mosasauridce. 



As a conclusion, it may be derived that these reptiles are not nearly 

 related to the Varanidce as has been supposed, but constitute a distinct order 

 of the streptostylicate group; that they arc primarily related to the Lacer- 

 tilia, secondarily to the Ophidia, and thirdly to the Sauropterygia; that they 

 present more points of affinity to the serpents than docs any other order ; and 

 their nearest point of relationship in the Lacertilia is the Varanida. or 

 Thecaglossa. 



Experience in paleontology has shown that generalized orders have been 

 the predecessors of the special groups of the existing fauna. The structure 

 of the Pythoiiomorpha, which has so much in common with orders well dis- 

 tinguished from each other, offers a hint of the character of the primary 



