In the beginning of this year Mr. R. C. Keun, formerly Consul of the Netherlands at the empire of Siam, presented the Leyden Museum with a small collection of Reptiles from the neighbourhood of Bangkok. As Mr. Keun, because of ill-health, resigned his honourable employment, he will not be in a position again to add other Siamese specimens to those we have already received, and it is therefore that I give a list of this valuable collection, the more valuable as the Reptiles of the Indian continent are very poorly represented in our Museum, those of Mr. Day’s precious collection ¹) being almost our sole representatives of the Indian herpetological fauna. In making up this list I follow the nomenclature and the arrangement adopted by Mr. G. A. Boulenger in his »Reptilia and Batrachia” in »the Fauna of British India” except in his adoptation of the genus Trimeresurus Lacépède. The sole characteristic that, according to Lacépède, separates the snakes of the genus Trimeresurus from all other Opisthoglypha and Proteroglypha is the peculiar arrangement of the subcaudals. This characteristic is not to be found in one of the species belonging to the genus Trimeresurus according to Mr. Boulenger. Moreover the species first described by Lacépède, viz. Trimeresurus leptocephalus (a snake in my opinion very closely related to Naja porphyriaca Shaw and Naja australis Gray, both agreeing in having the peculiar arrangement of the subcaudals described by Lacépède) can by no means be classed in the genus Trimeresurus according to Mr. Boulenger. I think it better to adopt Wagler’s genus Bothrops and, if it should be found desirable to preserve Lacépède’s genus Trimeresurus, I would substitute it for Wagler’s genus Pseudechis.