26 



PROCEEDINGS OF THE NATIONAL MUSEUM. 



vou GO. 



The distinctness of the two Varanid genera Varanus and San'twa 

 is clearly set forth by the enumeration of their more important char- 

 acters as contrasted in the two paralled columns below : 



Genus Varanus. 



1. Dorsal vertebrae without zygos- 

 pheneal articulations. 



2. Coracoid having two anterior 

 notches. 



3. Postorbital usually fused with 

 postfrontal. 



4. Hypophyses on first six or seven 

 cervical vertebrae, vestigal on the sev- 

 enth or eighth. 



5. First rib carried on the seventh 

 cervical. 



6. Humerus with gradually ex- 

 panded ulnar border at distal end. 



Genus San/iwa. 



1. Dorsal vertebrae having vestigal 

 z.vgosphene articulations. 



2. Coracoid having a single anterior 

 notch. 



3. Postorbital distinct from post- 

 fi'ontal. 



4. Hypophyses on first five cervical 

 vertebrae, vestigal on the sixth. 



5. First rib appears to have been 

 carried on the fifth cervical, possibly 

 the fourth. 



6. Humerus with abruptly expanded 

 ulnar border at distal end. 



A critical comparison of jSaniica, especially with the existing 

 members of the family, appears to show a few of the evolutionary 

 changes undergone bj'^ the Varanid skeleton since INIiddle Eocene 

 times. These are: 1. the loss of the vestigal zygosphene: 2, a reduc- 

 tion in the number of teeth in the jaws; 3, the complete coalescence 

 (usually) of the postfrontal postorbital bones: and 4, an increase 

 in the number of cervical vertebrae bearing hypophyses. 



The living members of Varanidae, Monitors as they are often 

 called, form a group of about 30 species, all belonging to the one 

 genus Varanus. Living members of this genus inhabit the tropical 

 parts of Africa, Southern Asia, Malasia, and Australia. All are 

 carnivorous in habit, feeding upon small backboned animals, insects, 

 and especially upon eggs, which they crush between their teeth while 

 holding them aloft. Most species live whollj^ upon the land and 

 some are arboreal. Others, especially those found along the Nile, 

 live about water and are excellent swimmers. The terrestrial species 

 are said^^ to haA'e "'a round tail and small external nostrils, but the 

 water species have the tail much flattened and the nostrils have large 

 cavities." 



Most of the species liA'e wholly upon the land. V. prasiniis is 

 supposed to be arboreal. Others, as V. salvator and F. niloticus, 

 owing to the fact of their tail being strongly compressed, are excel- 

 lent swimmers and deserve the name of water lizards. The terres- 

 trial species, as V. griseus, have rounded tails. The apparent ab- 

 sence of caudal vertebrae having high spinous processes suggest that 

 Saniwa was also a terrestrial species, having a rounded rather than 

 a flattened tail. 



s' Willistoii, S. W. Water Reptiles of the Past and rre.-^ent, 1914, pp. 144-145. 



