264 BULLETIN 58, ITNITED STATES NATIONAL MUSEUM. 



1853. Ncrodia Baird and Girakd, Serp. N. Am., p. 38 (type, N. sipedon). 



1853. Regina Baird and Girard, Serp. N. Am., p. 45 (type, R. leberis). 



1854. Amphiesma Dumeril and Bibron, Erpet. Gen., VII, p. 724 (type, A. 



stolatiiw). 

 188(). Bothrodytcs Cope, Proc. Amer. Philos. Soc, XXIII, 1880 (p. 495) (type, 



Amphirsma subminiatum). 

 1893. Ccratophallns Cope, Amer. Natural., XXVII, May, 1893, p. 483 (type, 



Natrix vittata). 

 1893. Diplophallus Cope, Amer. Natural., XXVII, May, 1893, p. 483 (type, N. 



piscator ) . 



This genus is quite commonly known as Tropidonotus Kuhl, but 

 the above synonymy shows how poor the status of that name is. 

 Natrix was estabhshed by Laurenti as early as 1768, and no difficulty 

 is encountered as to the type, since Flemino;, in 1822, before the name 

 Tropiclo7iotus was invented, designated iV. torquatus (Coluber natrix 

 Linnieus, or Natrix vulgaris Laurenti) specifically as the type. 



The genus Natrix, as here understood, has been variously sub- 

 divided into genera based upon the syncranterian or diacranterian 

 character of the dentition, the presence, or absence of scale pores, 

 and, lately, upon the structure of the intromittent organ, whether 

 simple or bifurcate, and whether provided with a papilla at the apex 

 or not. These structural characters are only known in a few of the 

 numerous species contained in the present genus, and any rational 

 attempt at subdivision must be postponed until they are investigated 

 in all the species. 



That the dentition in itself alone is not a satisfactory guide to the 

 proper segregation of the species into natural groups is shown by 

 Natrix vihalcari. By Boulenger this species is retained in the first sec- 

 tion of the genus, which he restricts as Tropidonotus proper, because 

 having the hinder maxillary teeth "gradually enlarged," against the 

 section Ampliiesrria having the "last two or three abruptly enlarged." 

 I have dissected out the maxilla of three specimens of this species and 

 would designate the last two teeth as "abruptly enlarged" in every 

 case. It is therefore impracticable to base a primary subdivision of 

 the group upon this character. 



On the other hand, the scale pores have only been recorded in the 

 case of very few species. Thus I can find no record as to whether 

 Natrix svnnhonis possesses them or not, and inclined as I am to regard 

 this character as indicating natural genera among these snakes, I am 

 unable to employ it at present. 



This leads to an inquiry into the closer relationship of the Japanese 

 species of this complex genus. As will be shown further on, Natrix 

 tigrinus is only subspecifically distinct from the mainland form N. 

 lateralis, which extends westward to the confines of Tibet. Natrix 

 vihal^ari belongs to another group of species which also extend 

 over China to the eastern Himalayas. It is not difficult to point 

 out Natrix khasiensis, from Assam, and Natrix craspedogaster, from 



