1895.] TEETH OF CEBTAIN POISONOUS SKAKES. 823 



viewed from the side, the lower half of the tooth is seen to be very 

 narrow and much attenuated. The apical portion of the tooth 

 is thus compressed antero-posteriorly. The groove is relatively 

 much larger than in the other genera (vide PI. XLVI. fig. 21), and 

 reaches to within a short distance of the apex, opening by a small 

 (anterior) aperture on the flattened surface of the tooth ; the 

 opening at the base of the tooth is large. Besides the two grooved 

 teeth there is also a small and much bent tooth, with a very obtuse 

 apex, situated on the outer edge of the maxilla slightly nearer to 

 the posterior end. 



Grenus Distika. 



Species examined : — B. cyanocincta. 



The glands are very similar to those of Enhydris (PI. XLVI. 

 fig. 1). The superior labial gland is greatly developed anteriorly, 

 and the poison-gland is much rounded posteriorly and slightly 

 constricted in the middle. The inferior labial gland is long aud 

 narrow, and the Harderian gland (PL XLVI. fig. 17) possesses a 

 larger posterior lobe than either Enhydris or Platurus. 



The maxilla (PI. XLVI. fig. 8) has two anterior grooved fangs, 

 the outer one a little posterior to the inner, which are propor- 

 tionately smaller than those in the two previous genera. There 

 is a considerable interspace, and then 8 smaller teeth forming a 

 somev\ hat irregular series. The first two or three only of these 

 teeth showed any indications of a groove \ This was so in the 

 maxillae of two specimens. 



In transverse section the grooved fangs are almost circular. 



Grenus Hydetjs. 



Species examined : — H. platurus and H. platurus var. altemans. 



The superior labial gland is not so large as in the three 

 previous genera. The poison-gland is partially under cover of a 

 mass of muscular tissue ; it is long and narrow, is partially con- 

 stricted in the middle, and extends invs'ardly a considerable distance 

 (PI. XLVI. figs. 3, 6, and 7). The Harderian gland is not dif- 

 ferentiated into two lobes, and is comparatively smaller than in 

 the other genera examined (PI. XLVI. fig. 16). 



The maxilla (PI. XLVI. fig. 10) possesses two anterior grooved 

 fangs, the inner one being slightly anterior in position to the outer 

 one. After a short interspace there is a series of 7 or 8 smaller 

 teeth of equal size; these latter are more crowded posteriorly. 

 The grooved fangs are slightly compressed laterally, and the groove 

 extends very far down the tooth and is tightly closed even when 

 quite close to the apex (PI. XLVI. fig 20). 



^ Boulenger (' The Fauna of British India : Eeptilia and Batrachia,' London, 

 1890) describes these posterior maxillary teeth as being grooved. Also in 

 P.Z. S. 1890, p. 618 ("Eemarks on a SkuU of Bistira cyanocincta from Ceylon"), 

 he mentions a large skull which possessed groo-ves on the mandibular teeth. 

 There were no grooves on any of the mandibular teeth in the specimens I 

 examined. 



