THE VARIATIONS IN THE NUMBER OF VER- 

 TEBRAE AND VENTRAL SCUTES IN TWO 

 SNAKES OF THE GENUS REGINA 



ALEXANDER G. RUTH VEX A XT) CRYSTAL THOMPSON 

 Museum of Zoology, University of Michigan 



It has been asserted that the number of large scales on 

 the ventral surface in snakes is the same or nearly the 

 same as the number of vertebras. Gadow (1901, p. 582) 

 asserts that the " skeleton segments correspond in num- 

 ber to the ventral and transverse scales of the skin, ' ' but 

 Jourdran (1903, pp. 25-26) has failed to find an exact 

 correspondence between the total numbers of scutes and 

 vertebrae in many specimens. According to the counts 

 published by the latter writer (1903, pp. 25-26), the dis- 

 crepancy may vary from 25 less to 53 more scutes than 

 vertebrae, and he concludes, 



On peut done conclure qu'il n'y a qu'une concordance tres relative 

 entre le squelette interne et la metamerisation externe des teguments. 



Unfortunately a study of Jourdran 's paper seems to 

 show that his counts of the vertebrae can not be relied upon. 

 Some of the skiagraphs are so poor that it is doubtful if 

 careful counts could be made from them, many of the 

 numbers given are estimates, the tail in some of the speci- 

 mens is broken, the disposition of the vertebrae is not 

 indicated, except when the number of ribs is given, and 

 the number of ribs given is in some cases much greater 

 than shown in the skiagraphs, apparently indicating that 

 the long transverse processes of the proximal tail ver- 

 tebrae have been counted as ribs. We believe that Jour- 

 dran 's work shows only that some discrepancy between 

 the number of vertebrae and the number of scutes may 

 occur. Grosser (1905, pp. 57-61) has pointed out that 

 there is a metameric arrangement of the ventral scales 

 except in the neck, anal and tail regions, so that dis- 

 crepancies must be confined to these regions. 



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