HERt»ETOLOGY OF JAPAN. 263 



to the studies of Cope and Boulenger, though much is to be learned 

 yet before a natural classification can be expected. 



This family is usually known as the Coluhridse., but, as will be shown 

 further on, the generic name Coluber belongs to the typical genus of 

 the so-called Viperidse. 



The distinctive characters of the four subfamilies recognized among 

 the natricid snakes occurring in Japan and adjacent territory have 

 been tabulated as follows: 



a^ Hypapophyses present throughout the vertebral cohimn (figs. 223-225). 



6' All maxillary teeth solid Natricin.e, p. 263. 



b'^ Posterior maxillary teeth grooved Homalopsin.e, p. 299. 



d^ Hypapophyses absent in posterior dorsal vertebrae (figs. 226-228). 



¥ All maxillary teeth solid Coronellin.e, p. 306. 



b'^ Posterior maxillary teeth grooved Boigin^, p. 381. 



Boulenger has shown that the question whether the haBmal proc- 

 esses are present on the posterior vertebrae or not can be easily 

 ascertained by making an incision along the belly in the posterior 

 fifth of the body, pushing aside the viscera, and disarticulating the 

 backbone by bending the body dorsally. The two styles of vertebrae, 

 with or without the lower median process, are shown in the accom- 

 panying figures. It should be remarked, however, that recently con- 

 siderable doubt has been thrown on this character as to whether it 

 is of the fimdamental importance usually attributed to it, or not. 



Subfamily ]Sr^^TRICI]Sr^S:. 



The Natricinae are without grooved teeth in the posterior part of 

 the upper jaw. 



Our species, although sometimes with the nostrils placed rather 

 high, never have them on top of the snout, and the internasal shields, 

 though often small and narrowed anteriorly, are in pairs and join the 

 rostral. The scales are strongly keeled. 



Only two genera are known from our territory, which may be dis- 

 tinguished as follows : 



a' Subcaudals divided; postoculars well developed, separating temporals from orbit. 



Natrix, p. 263. 



a^ Subcaudals single; postoculars rutUmentary. the temporals apparently entering the 



orbit Achalimts. p. 294. 



Genus NATRIX" Laurenti. 



1768. Natrix Laurenti, Syn. Kept., p. 73 (type, N. vulgaris^ Coluber natrix). 



1822. Tropinotus Kuhl, Isis, 1822, p. 473 {nomen nudum). 



1826. Tropidonotus H. Boie, Isis, 1826, p. 205 (type, T. natnx). 



1843. Rhabdophis YiTziNGEU, Syst. Rept., p. 27 (type, T. subininiatus, Schlegel). 



1843. Steirophis Fitzixger, Syst. Rept., p. 27 (type, T. chrysarcpts Kuhl). 



1852. Hydrophilophis Schmidt, Abh. Naturw. Ver. Hamburg, II, Pt. 2 (substitute 

 for Tropidonotus). 



° Signifying a water snake; literally, a swimmer. 



