132 



VENOMS 



on the upper surface of the snout, between the nasal shields. The 

 eyes are always very small. 



The number of species at present known is considerable ; they 

 are divided into ten genera. We shall confine ourselves here to 

 mentioning the principal diagnostic characters of these genera, 

 and to descril)ing the most common species. 



Fig. 77. — Skull of Hydrus idaturus. 

 (After G. A. Boulenger, op. cit.) 



(1) Hydrus. 



(Pig. 77.) 



Maxillaries longer than the ectopterygoids, not extending 

 forwards as far as the palatines; poison-fangs grooved, rather 

 short, followed, after an interspace, by 7 or 8 solid, backwardly 



