and Revision of the South American Elaps. 165 



colours : for instance, Simotes purpurascens, Tropidonotus quin- 

 cunciatus, Erythrolamprus venustissimus, &c. The latter species 

 especially, having the same system of coloration as Elaps (with 

 black rings on a red ground-colour), and inhabiting the same 

 parts of the globe, shows a strikingly similar gradation of 

 varieties, but with the physiognomy of the head always precisely 

 the same. 



I have again examined the ninety specimens of South Ameri- 

 can Elaps in the Collection of the British Museum, and com- 

 pared them with Prof. Jan's account. Two only of the species 

 figured by him could be clearly made out, whilst many other 

 specimens approached to some of the figures, and nearly twice 

 as many could not be referred to any of his specific categories. 

 Now, if we consider that there were examined the specimens of 

 a part of the British, German, French, and Italian Collections 

 only, that these specimens were collected in the most accessible 

 parts of South America, that scarcely two specimens perfectly 

 agree with each other, to what amount will the number of spe- 

 cies finally reach — species of the geographical distribution of 

 which we know extremely little, which never were observed in 

 nature, and which for the greater part show precisely the same 

 shields of the head ! I think the synonymy of some species of 

 snails ought to teach us a different lesson. It would be ridicu- 

 lous to deny that different species of Elaps inhabit the vast 

 continent of Tropical America, and even many more than we at 

 present know ; but we can only cautiously introduce new forms 

 into the list of species ; and I think myself at liberty to do so 

 by a combination of the following characters only : — 



1. If there is a striking difference in the shape or in the 

 arrangement of the shields of the head. The extent of the sixth 

 upper labial shield (to or not to the occipital) does not constitute 

 a specific difference of itself. 



2. If there is a great difference in the general habit of the 

 snake, or in the proportions between the single parts. The 

 number of the ventral and caudal plates is in proportion to the 

 length of the trunk and of the tail. We find that the number 

 of ventral plates in those species of Elaps of which we have the 

 best knowledge from a great number of specimens, is subject to 

 a variation of seventy and more ; therefore we cannot deduce 

 from it alone a specific character, without having examined 

 several specimens. 



3. If there is such a difference in the distribution of the 

 colours that we cannot refer it to a typical coloration of one of 

 the known species*. 



Prof. Jan has illustrated the new species with coloured plates. 

 * Cf. Proc. Zool. Soc. 1859, p. 82. 



