13. COLIJBRIDM 



The following facts also will be of aid in the determi- 

 nation of specimens: 



1. Any red in the coloration indicates that the speci- 

 men belongs to one of the subspecies of T. sirtalis or to 

 T. o. ordinoides or T. o. atratus. 



2. Red on the upper surface of the head seems to be 

 peculiar to the subspecies of T. sirtalis. 



3. Red on the belly or in the dorsal line is distinctive 

 of T. o, ordinoides and T. o. atratus, or rarely T. s. 

 farietalis. 



4. The members of the sirtalis group have a much 

 larger eye and longer posterior genials than are found in 

 the subspecies of T. ordinoides, with the possible exception 

 of T. o. hammondii. 



5. The members of the sirtalis group practically 

 always have 19 — 19 — 17 rows of scales and a single 

 prcocular. 



6. In the subspecies of T. ordinoides 2 1 rows of scales 

 are almost always present, except in T. o. ordinoides and 

 T. o. atratus. 



7. Two preoculars are most frequent in T. angustiros- 

 tris and T. o. biscutatus, but are frequent in T. o. ham- 

 mondii and T. o. ordinoides. 



8. Absence of the dorsal stripe occurs only in four of 

 the subspecies of T. ordinoides — viz., hammondii, couchii, 

 ordinoides, and atratus, — and is usual in only hammondii 

 and couchii. 



The garter-snakes are the most abundant of our ser- 

 pents. Where conditions are especially favorable they may 

 be found in vast numbers. They are ovoviviparous, and a 

 single female has been known to produce as many as 78 

 to 80 young or as few as four at a time. Mating occurs 

 in the spring. The young are born in July, August or Sep- 

 tember. They are extruded singly, each coiled within its 



