296 MR. S. C. SARKAU ON THE BUCCAL GLANDS 



organs, such as the poison gland, its duct and poison fangs, taken 

 concurrently. So far as I ani aware, this is the iirst research on 

 these lines. 



The presence of grooved teeth in the posterior region of the 

 maxilla was first observed and discussed by Thomas »Suiith (11) 

 and later by J. G. Fischer. In the year 1892, Niemann (6) 

 published an account of the structure and relationships of the 

 glands of the upper lip in general, but he described only three 

 tj'pes of the Opisthoglypha, His work on this group is very 

 sc^inty, while the diagrams are insufficient and wanting in detail, 

 but the connection of the duct and the groove of the fang is 

 well emphasized. In 1895, West (15) published a detailed 

 description of the buccal, glands and teeth of opisthoglyphous 

 snakes. His paper made a considerable advance in the 

 knowledge of this subject; his observations are still looked upon 

 as a good groundwork, and hiswoi'k is quoted by various authors. 

 His descriptions, however, relate only to morphology. I have 

 described four riiore genera of this group — CJir>/sopcIea, IVrboji/iis, 

 rsamniopJiis. and Cerberus; the tirst two were not mentioned at 

 all by AVest, and of the other two he gave only a short description 

 of the teeth. 



It was in 1896 that -Boulenger put forward an account of the 

 pi'obable evolution of the Opisthoglypha from the Aglypha. He 

 pointed out that in the higher genera of the Aglypha the series 

 of teeth in the jaw shows an increase in size from in front 

 backwards, so that we are gradualh- introduced to the opistho- 

 glyphous condition, with a lai'ge fang in the posterior region of 

 the jaw. In the higher types of both the Opisthoglypha and 

 Proteroglypha this fang is always distinctly bigger than the 

 tooth in front of it. Therefore in my discussions of the 

 probable evolution of the fang of the Opisthoglypha from the 

 somewhat enlarged posterior tooth of the Aglypha, 1 have 

 selected those snakes in the Aglypha in which the posterior 

 tooth is clearly larger than the preceding one — e. g.. Tropidonofus 

 and Lt/codoii. 



Among recent papers on the Ophidia, those of j\Iary Phisalix 

 are the most important. In her work (9) she discusses the 

 accounts given by various authors, and she has attempted to 

 an*ange the members of this group in an ascending series on 

 evolutionary lines, according to the disposition of the" teeth. In 

 this paper I have attempted a like task, but my series difiers 

 from hei-s in that I have tried to select for consideration only 

 those Aglyphodont forms in which the last tooth has become 

 markedly ditlerent from the rest. Also I have discussed what 

 I consider to be the highest grade of evolution in the Aglypha — 

 i. e., the condition presented by those types in which the last 

 tooth has acquired two cutting-edges int^tead of only one. Mary 

 Phisalix does i\ot continue her series beyond those with one 

 cutting-edge. It should be noticed that my diagram of Tropido- 

 notus stolatus (text-fig. 10) differs from hers (see p. KU. ref. 9). 



