SYNOPSES AND DESCRIPTIONS. 25 



the dark color is produced toward the throat. On account of the amount 

 of variation of this species in different localities, it is hardly to be separated 

 from the preceding. Canada to Central America. 

 sirtalis. Rows 19. Spots 70—90. Ventrals 140—165+60—85 pairs. 



Mississippi Valley and eastward. 

 marcidnm. Rows 21. .Spots 50 — 75. Ventrals 145 — 175+50 — 90 pairs. 



Texas to Mexico. 

 parietalis. Rows 21. Spots 70—110. Ventrals 160—1854-50—90 pairs. 



Valley of the Missouri and westward. 

 infernalis. Rows 17—19. Spots 100—120. Ventrals 145—175+75—95 



pairs. California and northward. 

 collaris. Rows 19. Ventrals 151— 165 + 58— 84 (Jan.) Mexico to Panama. 

 ordinatus. Agrees with .sirtalis, hut has the lower scries of spots more 



distinct, while the stripes arc* almost obsolete, and is found in various 



isolated localities of the same district, as Alabama, South Carolina, 



Martha's Vineyard, and Nova Scotia. 



Tropidonotus sipedon, pi. II, Jiff. 3. 



Coluber si pedon Limn'; 1758, Syst. Nat., ed. X, 219. 

 Tropidoxotus sipedon Hblbrook, 1842, A*. A. Herp. IV, p. 6, pi. 29. 



Stout, fusiform, belly broad; head distinct, narrow forward; tail smaller 

 than the body, tapering. Eye medium, pupil round. Mouth-cleft deep, 

 abruptly curved near the angle. Nine head-shields. Rostral low, broader 

 than high. Nasal in two parts, nostril between. A loreal. One anteor- 

 bital, sometimes two. Postorbitals two to four. Temporals 1+2, large. 

 Labials 8 (7—9), sixth and seventh large. Infralabials 10 (9—11), fifth 

 and sixth large. Submentals two pairs, large, not in contact with the 

 mental. Scales strongly keeled, in 23 to 1*5 rows, dorsal narrow, outer 

 broader than long, keeled to smooth. Ventrals 130 — 155. Anal divided. 

 Subcaudals 40 — 75 pairs. 



Varying from ashy to very dark brown, or to brownish-red; with three 

 series of dark-edged brown spots; dorsal about ten scales in width, varying 

 in shape from irregular rounded to nearly square, distinct or confluent with 

 the lateral into transverse bands, which widen toward the vertebral rows. 

 There are usually twenty-five to thirty spots on the flank, wider than long, 

 and from fifteen to twenty on the tail. Commonly the spots on the flanks 

 are more or less opposed and confluent anteriorly, but posteriorly alter- 



