364 ON THl-: DORSAL SCALE-ROWS IX BRITISH SNAKES. 



hjcns ater Giintb. it is normal for the male to have 17, and the 

 female 19 seale-rows on the anterior two-thirds of the body, 

 caudad to whicli the number of rows is reduced to 15 in both 

 sexes. The sexual dimorphism in this case, which so amply fulfils 

 Dr. Ruthven's supposition, led to the sexes being described as 

 two species, Pseudohoodon alhopunctatus and P. hrevicaudatus 

 Andersson. In the female of this snake the reduction from 19 

 to 17 scale-rows is effected by the convergence of series VIII. 

 and IX., two-thirds down the body, and that from 17 to 15 by 

 the convergence of series VIII. and VII. about nine-tenths down. 

 In the male the reduction to 17 rows is accomplished on the neck, 

 and that from 17 to 15 takes place three-quarters of the way 

 down the body, also by the convei-gence of the Vlltli and Vlllth 

 series; even this caudad reduction is therefore further advanced 

 in the male than in the female, thus completing the sexual 

 dimorphism of this unique species. 



