ART. a3. AN EXTINCT VARAXID LIZARD GILMORE. 23 



groove which extends for a short distance up on the shaft of the 

 bone. The epiphysis of the distal end of tliis bone is as distinctly 

 defined as in the living Varanus. The broken end of the shaft shows 

 a large medullary cavity, now filled with calcite. The transverse 

 diameter measures 13.2 mm. ; the fore and aft diameter at the center 

 is 8.5 mm. 



Tibia. — The proximal half of tlie left tibia (see pi. 2, fig. 2) shows' 

 the same broad expansion of the upper end with flattened anterior 

 surface, and the same contracted subtriangular shaft at the middle 

 "with large medullary cavity as in the living Monitor. In fact, I 

 fail to find any characters by which it may be distinguished from 

 Varanus. The proximal end of the tibia has a greatest transverse 

 width of 13 mm. 



Ribs. — In the three blocks of matrix containing the presacral 

 vertebrae there are parts of more than 18 ribs (see pi. 3, figi. 2). 

 several being nearly complete. All of the ribs appear to be single 

 headed. A rib lying in the matrix near the right coracoid has a 

 vertically expanded head, indicating that it probably pertains to the 

 posterior cervical series, the expansion of the head corresponding 

 to the elongation of the parapophj'ses in this region of the neck. 

 The thoracic ribs, however, do not have any appreciable enlarge- 

 ment of the proximal end, which is cupped for articulation with 

 the hemispherical parapophyses of the dorsal vertebrae. The proxi- 

 mal half of the larger thoracic ribs is flattened both fore and aft. 

 becoming subcylindrical as the distal end is approached, which is 

 slightly expanded. These ribs, in fact, all of the ribs, appear to be 

 moderately but regularly curved from end to end. 



DISCUSSION OF THE FAMILY, AND GENETIC RELATIONSHIPS OF 



THE GENUS SANIWA. 



Family VARANIDAE. 



Postorbital bar incomplete; temporal arcade complete; supra- 

 temporal fossa not roofed over by dermal bones; single premax- 

 illary bone; nasals coalesced and narrow; infraorbital vacuity 

 bounded by the pterygoid, palatine, and ectopterygoid, the maxil- 

 lary being excluded; palate toothless; hameal surfaces of the dor- 

 sal vertebrae broad, flat, and devoid of carina;.* vertebrae usually 

 without zygosphene or zygantrum, when present a vestigal zygo- 

 spliene only. No dermal ossifications. 



In the characterization of the family Varanidae as given above 

 1 have selected from the definitions of Lydekker,^^ Boulenger," 

 and Fejervary^* such parts of their family characterizations as 



« Catalogue of Fossil Reptilia and Amphibia in British Museum, pi. 1, 1888, p. 281. 

 "Fauna Brit. India, Ropt. and Batr.. London, 1890, pp. 160-161. 

 " Ann. ]\Ius. Nat. Hung., vol. 16, 1918, p. 3G5. 



313G— 22— I'roc.N.M. Vol .6( t 4 r, 



