G!)6 MR. ST.GEORGE MIVART ON PLETHODON PERSIMILIS. [Jutie 27, 



That a Newt from the south-eastern coast of Asia should resemble 

 some North-American tailed amphibian could not have been so sur- 

 prising, considering the xlmerican affinities of the Japanese forms ; 

 but that a species from Siani proper should resemble almost com- 

 pletely a genus otherwise exclusively North American and posses- 

 sing no representative in the Palserctic region* was a circumstance 

 truly remarkable. 



Mr. Wallace has indeed suggested an explanation (by means of 

 certain presumed geographical mutationsf) of the discrepancy exist- 

 ing between the ophidian and batrachian populations of Japan ; but 

 it seemed to me difficult to account in any similar way for the phe- 

 nomenon under consideration. 



It is true that though Plethodon is unrepresented in the Old 

 "World, unless by the so-called PL jjemimilis, yet the North-American 

 genus Spelerpes has a near relative in Europe in the Geotriton c/enei 

 of Tschudi|, and has recently been extended to the Neotropical re- 

 gion by Professor Peters§ ; yet this hardly lessens the anomaly pre- 

 sented by the appearance of such a genus as Plethodon in the true 

 Indian region. Accordingly I applied to Dr. Giinther for any addi- 

 tional information I could obtain concerning the typical specimens. 

 He at once, with great kindness, placed me in possession of facts 

 which considerably altered the aspect of the question. 



Mr. Mouhot, from whom the specimens were received, terminated 

 his collections in the mountains of Laos, a very lofty region, to the 

 north-east of Siam proper. The last specimens received from Mr. 

 Mouhot were from that locality, and were without any notes, having 

 been brought down after his death by his servants. The typical 

 specimens of PI. persimilis were received also without any notes ; 

 and Dr. Giinther entertains no doubt that they formed part of his 

 last collection, i. e. that they came from the Laos Mountains. 



Supposing, as I have little doubt, that such was really the case, 

 then the probability of finding American forms is largely increased, 

 as we are, in these mountains, uo longer in Siam proper, and, more- 

 over, at an altitude such as fairly to warrant the expectation of the 

 appearance of Palaearctic animals. That Japanese forms (i. e. Uro- 

 dela allied to certain American kinds) should here make their ap- 

 pearance would not then be so surprising, the more so as Dr. Giin- 

 ther informs me that the reptiles of the island of Formosa have con- 

 siderable American affinities ; and though Newts have not yet been 



* Dr. Giinther, in his highly interesting and instructive paper on the " Geo- 

 graphical Distribution of Reptiles," says, speaking of Batrachians, " Palaearctic 

 and Nearctic regions resemble each other more than any third" (P. Z. S. 1858, 

 p. 390). 



t Nat. Hist. Review, vol. iv. 1864, p. 114. 



t Batrach. pp. 59 & 94, t. 2. f. 3. 



§ Namely his Spelerpes (Oedipus) adspersus from Bogota (Monatsberichte der 

 k. p. Akad. der W. z. Berlin, 1863, p. 468). But as allied forms are being dis- 

 covered in the tableland of Mexico (e. g. Spelerpes cepfialicus, S. osculus, and S. 

 lineolus, Cope, Proc. Acad. Nat. Sc. Philad. 1865, pp. 196, 197), it is not improbable 

 that other species will be found to have extended into, or to be represented by 

 modified descendants in, the mountain-regions of Northern South America. 



