39. MATRIX— 4-0. THAMNOPHIS 



In Lower California, it was first secured by Xantus near 

 Cape San Lucas. It appears to be the most abundant snake 

 of the country immediately surrounding San Jose del Cabo, 

 and has been taken also at Miraflores, Agua Caliente, and 

 Santiago, all in the Cape Region. Mr. Belding's specimens, 

 recorded by Yarrow as taken at La Paz, really came from 

 the San Jose River (Belding MS.). 



Habits. — This is a true water snake. Individuals had 

 eaten pollywogs and small fish (Mugil brasiltensis) . 



Genus 40. Thamnophis 



Thamnofhis Fitzinger, Syst. Rept., 184-3, p. 26 (type, saurita). 

 Eutamuj Baird & Girard, Cat. N. Amer. Rept., Pt. I, Serp., 1853, 

 p. 24 (type, saurita). 



The body is more or less elongate, usually rather slen- 

 der, with moderately long, tapering tail, and head distinct 

 from neck. The cephalic plates are normal. The nasals 

 are not united. One or two (rarely three) preoculars, and 

 one to four, usually three, postoculars are present. The 

 temporals are normally 1+2, but may be 1 + 1, 1+3, 1+4, 

 2+2, or 2+3. A loreal normally is present, rarely absent. 

 The scales are keeled, in 1 7 to 23 rows. The anal plate nor- 

 mally is undivided, but in rare individuals is divided as in 

 the genus Natrix. There are no scale pits. The urosteges 

 are in two series. The eye is moderate or small, with round 

 pupil. 



Fourteen kinds of garter-snakes from Western North 

 America now are recognized. Although the several species 

 and subspecies may often be distinguished at a glance by 

 one familiar with their several characters, the amount of 

 individual variation is so great that it is quite impossible to 

 make a key which will properly refer all specimens. The 

 following synopsis will, I believe, usually serve its purpose, 

 bat should not be trusted too implicitly. 



