1895.] TEETH or CERTAIN POISONOTTS SNAKES. 815 



surroundiug the grooved tooth, or becoming enlarged it com- 

 municates with the cavity surrounding tlie tooth by an aperture 

 about equal iu diameter to that of the duct. This opening is 

 always towards the outer side of the grooved tooth (the first 

 one when more than one is present), and may be situated either 

 at the base of the tooth or a little way from it (PI. XLIV. fig. 15 ; 

 PI. XLV. fig. 5). It will be seen from the above that the duct 

 is not itself in du'ect communication with the groove of the 

 tooth, but that the two communicate through the mediation of the 

 cavity enclosed by the muscular folds surrounding the tooth, which 

 are imited in front. Consequently the loss of the tooth does not 

 cause any injury to the duct, and in a short time one of the reserve 

 teeth takes the place of the lost one. There are usually about 

 half a dozen reserve teeth in successive stages of development 

 behind the functional one, and they are in no way connected with 

 the duct until called upon to replace a tooth that has been damaged 

 or lost. The reserve teeth are posterior and internal to the 

 functional ones, and are developed under cover of the expanded 

 anterior extremity of the trauspalatine bone ; their positions are 

 indicated in fig. 11, PI. XLV. 



The grooved teeth are situated at the posterior extremity of the 

 maxilla, and their number varies from one to three in different 

 genera and species. They are generally much larger than the 

 otb.er maxillary teeth and also straighter, though, hke them, they 

 are directed backwards at a considerable angle. Some of the teeth 

 are almost circular in section, others compressed, and all are more or 

 less irregular. A few have distinct cutting-edges on the posterior 

 face of the tooth, e. g. LeptocUra rufescens (PI. XLV. fig. 12), Tham- 

 nodynastes nattereri (PI. XLV. fig! 16). The groove is situated 

 as a rule on the antero-external face of the tootih, though in three 

 observed cases it is directly external in position, viz. — Dryophis 

 prasinus (PL XLIV. fig. 12), D. mycterizans (PI. XLIV. fig. 13), and 

 Oxyhelisfulrjida (PI. XLIV. fig. 21). In some the groove is almost 

 closed, whereas in others it is widely open. It also varies in its 

 extent down the tooth, for whereas in a few it almost reaches the 

 extreme apex, in others, of which Bipsas irregularis is a notable 

 example, it does not extend more than two-thirds of the way 

 down. 



The mandihidar teeth are as a rule about the same size and often 

 more numerous than the maxillary, and they decrease in size in an 

 antero-posterior direction; the most anterior teeth are more 

 crowded and also placed in a more upright position than the 

 maxillary teeth. The ciu-vature is generally confined to the 

 upper half of the tooth, and they are never recurved at the apex 

 as is so often the case with the maxillary teeth. 



The Harderian gland in this group of Snakes is very variable ill 

 form and size, and may or may not be visible on removing the skin. 

 In some it is a small elongated glandular mass, whereas in others 

 it possesses two or three lobes and is of considerable bulk, A 

 portion of it is always situated behind the eye, in the orbit. 



52* 



