COLUBER. POISONOUS SERPENTS. 225 



series as long as that which terminates it. The colubers, like other 

 true serpents, have two longitudinal rows of teeth on the roof of the 

 mouth, extending along the palatines and pterygoids : the genus Oli- 

 godon appears to form the sole exception to this rule. In the Dryinus 

 nasutus M. Duvernoy(l) has noticed a few small teeth on the trans- 

 verse bone or external pterygoid, as well as on the internal pterygoid. 



In certain genera of non-venomous serpents, as Dryophis, Dipsas, 

 and Bucephalus, in which the superior maxillary teeth increase in size 

 towards the posterior part of the bone, the large terminal teeth of the 

 series are traversed along their anterior and convex side by a longitu- 

 dinal groove. In the Bucephalus capensis{2) the two or three posterior 

 maxillary teeth present this structure, and are much larger than the 

 anterior teeth or those of the palatine or premandibular series ; they 

 add materially, therefore, to the power of retaining the prey, and may 

 conduct into the wounds which they inflict an acrid saliva, but they 

 are not in connection with the duct of an express poison- gland. The 

 long grooved fangs are either firmly fixed to the maxillary bones or 

 are slightly moveable according to their period of growth ; they are 

 concealed by a sheath of thick and soft gum, and their points are 

 directed backwards. The sheath always contains loose recumbent 

 grooved teeth, ready to succeed those in place. 



In most of the Colubri each maxillary and premandibular bone 

 includes from twenty to twenty-five teeth : they are less numerous in 

 the genera Tortrix and Homalopsis, and are reduced to a still smaller 

 number in the poisonous serpents, in the typical genera of which the 

 short maxillary bone supports only a single perforated fang. 



96. Poisonous Serpents. — The transition to these Serpents, which 

 was begun in the Bucephali and allied genera with grooved maxillary 

 teeth, is completed by the poisonous serpents of the genera Pelamis, 

 Hydrophis, Elaps, Bungarus and Hamadryas, which latter genus, as 



(1) Annales des Sciences Nat. torn, xxvi, p. 43. 



(2) Having been favoured by Dr. A. Smith with specimens of the Bucephalus Capensis the 

 results of my dissections are confirmatory of his own as regards the absence of a poison -appa- 

 ratus in that snake : the ordinary saUvary gland is large, especially at its posterior part which 

 transmits its secretion by many pores into the sheath of the grooved fangs. The presence of a 

 distinct poison-gland and duct communicating with the grooved posterior teeth requires to be es- 

 tablished before the Serpents with these teeth can be ranked with the poisonous genera. 



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