BUCCAL GLANDS OF THE OPISXHOGLYPHA. 295 



21. A Comparative Study of the Buccal Grlauds and Teeth of 

 the Opisthoglypha, and a Discussion on the Evolution 

 of the Order from Aglypha *. By Sushil Ch. Sarkar, 

 F.Z.S. 



[Received December 22, 1922 : Read March 20, 1923.] 

 (Text-figures 1-29.) 



Intro chbction. 



The comparative anatomy of the buccal glands, teeth, and the 

 problem of the evolution of the opisthoglyphous Snakes forms the 

 subject of this paper, and was suggested to me by Professor G. E, 

 Nicholls, under whose supervision the investigation was begun 

 in the Biological Department of King's College for Women, 

 Household and Social Science Department. After the research 

 had been in progress for three months Dr. Nicholls had to leave 

 for Australia, and since then the work has been carried on under 

 Miss Philippa C. Esdaile, D.Sc, F.Z.S. It is wdth pleasure that I 

 acknowledge my indebtedness to Dr. Esdaile for her invaluable 

 advice and criticism during the progress of the work. 



I wish also to express my obligation to Professor Dendy and 

 the Government Grant Committee of the Royal Society of 

 .London for a grant-in-aid. Lastly, I have to thank Miss Alfreda 

 Newton for her kind assistance in cutting series of sections of 

 a large number of heads of snakes, and also for taking photo- 

 graphs of specimens and sections. 



Historical Facts, 



The snakes chosen as types in this research belong to the 

 Aglypha and Opisthoglypha. i. e. two of the three divisions of 

 the Family Colubridae. These differ from one another by the 

 fact that in the Aglypha all the teeth in the maxilla are solid, 

 Avhilst in the Opisthoglypha one or more grooved teeth are 

 present in the posterior region. The members of the latter 

 group are more or less poisonous. 



The group Opisthoglypha is of special interest in that it is 

 considered to be the connecting-link between the Aglypha on the 

 one hand and the Viperida3 (with grooved teeth at the anterior 

 end of the jaw) on the other ; the group Proteroglypha is 

 believed to have developed independently and directly from the 

 former. Although the possible evolution of the Opisthoglypha 

 was pointed out by Boulenger, no research to verify his 

 statements has been attempted in connection with the important 



* Thesis submitted for Ph.D. degree, Universitj' of London, June 1922. 



20* 



