1895.1 TEETH OF CEiairAiif toisoirotjs snakes. 813 



I always find them to conform to the tubulo-racemose type, and 

 to consist of small polygonal lobules arranged round the branches 

 of a duct. Moreover the nuclei are situated at the base of the 

 cells and not in the middle, this being most markedly the case in 

 the Proteroglypha, where the nuclei are more or less flattened 

 against the bases of the cells. 



The Snakes treated of in this paper belong to the Colubridse, 

 and all come under two of Boulenger's groups, viz. — the 

 Opisiho(jlypha and the Proteroglypha. Of the latter only the Marine 

 Snakes (the Hydrophiina) are here dealt with. Unfortunately 

 many of the specimens were insufficiently preserved for histological 

 purposes. They formed part of the teaching collection at the 

 Eoyal College of Science, which Professor Gr. B. Howes kindly 

 placed at my disposal, together with specimens that he obtained 

 for me from the Natural History Museum and elsewhere. My 

 very best thanks are also due to him for suggesting this investigation, 

 and for many hints and much valuable information received during 

 its progress, and to Mr. Gr. A. Boulenger for kind assistance. 



COLUBEID^. 



Opisthoglxpha. 



Whether Opisthoglyphous Snakes should be regarded as truly 

 poisonous or not is a matter over which there hangs considerable 

 doubt. The gland in these Snakes which communicates with 

 the posterior grooved teeth is functionally ' very similar to 

 that gland which is in communication with the fangs of the 

 Proteroglyphous Snakes ". In structure it is somewhat different, 

 but I refer to it throughout this paper as the " poison-gland," as it 

 is undoubtedly the homologue of that structure present in the 

 Viperine and Proteroglyphous forms. It is of a more or less oval 

 form, always situated posterior to the eye, and as a rule a little 

 below it, its anterior extremity never reacliing beyond the middle 

 of that organ. 



The superior labial gland is an elongated band of glandular 

 tissue extending along the whole of the upper jaw and skirting 

 the lower edge of the poison-gland, encircling its lower half in 

 such a manner that the two glands are often superficially 

 indistinguishable, apjjarentlv forming one continuous structure 

 (PI. XLIV. fig. 11 ; PI. XLV. fig. 10). Both glands exhibit a 

 superficial lobulation, the lobules being polygonal in form and 

 generally a little larger in the superior labial gland ; there is often 

 also a marked difiei'ence in colour between the two glands, the 

 poison-gland being of a much lighter colour — generally a light 

 yeUow (in spirit-specimens), whilst the superior labial gland inchnes 



^ The bite of Lryophis and other Opisthoglyphous Snakes has been proved by 

 several observers to be fatal to small animals. 



' The former is more or less embedded in the superior labial gland, whereas 

 the latter is almost isolated from it, the superior labial gland here attaining its 

 greatest bulk at the anterior extremity of the jaw, 



Pboo. Zooi. Soc— 1895, No. LH. 52 



