322 SNAKES OF CEYLON. 



* Platylepas sp. (?) (Darwin) on Enhydrina valakadyen. 



* Platylepas ophilus (Lankester) on species of Hydrophis. 



* Platylepas krugeri (Pilsbury). 



* Dichelasphis grayi (Darwin). 



Lepidosis. — As already remarked the shielding of the head 

 and scaling of the bodies of hydrophids are subject to a 

 variation which is far in excess of what one sees in the most 

 variable land snakes. Gunther in 1864 wrote that herpeto- 

 logists who preceded him, with the single exception of Gray, 

 had erred in supposing the numbers of species of seasnakes 

 to be far fewer than they in reality are. If that remark was 

 true fifty years ago, Gunther and succeeding herpetologists 

 have amply redeemed the aspersions cast upon their fore- 

 fathers by erring in a contrary direction. Many an indi- 

 vidual exhibiting a slight deviation from a previously well- 

 known species has been acclaimed as a new species, even by 

 our best herpetologists. When one sees the large range of 

 costal rows round the neck and body, of the ventrals between 

 the neck and vent, and of the great variation in the head 

 shielding of so distinctive a species as Enhydrina valakadyen, 

 one should be prepared to expect a similar degree of variation, 

 in some other species of hydrophids with less distinctive 

 characters. 



Dentition. — Maxillary : Prsenodal. Two canaliculate fangs 

 are placed side by side anteriorly, each with a scar on its 

 anterior face. Postnodal. From 1 in Platurus to 17 in 

 Polyodontognathus cserulescens ; isodont, or feebly scaphiodont. 

 With shallow grooves on their antero -external faces . Palatine : 

 5 to 10 ; anododont, isodont. A short edentulous space 

 posteriorly in some. Pterygoid : 7 to 27 ; anododont, scaphio- 

 dont. The posterior half to third edentulous. Mandibular : 

 9 to 26 ; anododont, scaphiodont ; grooved on their antero - 

 external faces. 



Distribution. — Indian and Pacific Oceans. Many appear 

 to have a very local distribution, others, notably Hydrus 

 platurus, a very extensive one. 



* Have only been found attached to seasnakes. 



