ART. 25 



CHINESE AMPHIBIANS AND EEPTILES STEJNEGER 



67 



scale formulas as given above N. pisr.ator has a relatively shorter 

 body and longer tail, but no absolute line can be drawn; it also has 

 the fourth and fifth supralabials entering the eye, but we have 

 numerous examples of N. annulaHs^ etc., in which the fifth labial 

 touches the eye, though possibly not to the same extent. 



In .V. piscator, moreover, the second row of temporals usually con- 

 sists of only two scales. Concomitant with this we find that the 



number of ventrals and subcaudals in JSfatrix piscator, percarinata, and an- 

 nularis tased on published records of 12 specimens 



Fig. 5. — Xumlier of ventrals : 



Natrix piscator, 43 records. 



-_-_____ Xatrix peircarinata, 8 records. 

 2\atrix annularis, 21 records. 



Fig. 6. — Number of subcaudals : 



Satrix piscator, 30 records. 



________ y'atrix percarinata, 6 records. 



Xatrix annularis, 18 records. 



(normally) eighth supralabial is pentagonal and much higher, with 

 an angular upper border much greater than the labial border, while 

 in A''. annu7a7'is this shield is nearly quadrangular with parallel up- 

 per and lower borders. These characters in conjunction with the 

 strongly marked color-pattern of the postocular region in N. pis- 

 cator suffice in all cases to identify this common species. 



