75 



2. Two labials entering the eye ; ventrals 



182 — 196; subcaudals 99 — III 13. T. Itypomelas p. 83. 



c. Scales in 19 rows. 



1. A single anterior temporal 14. T. conspicillatus p. 83. 



2. Two anterior temporals. 



+ Scales of outer row smooth or feebly 

 keeled; frontal one time and a half 

 to one time and three fourths as long 



as broad l'^. T. triangtiligerns p. 84. 



-|-+ Scales all strongly keeled; frontal one 



time and one third as long as broad. 16. T. peter si p. 85. 

 B. Two or three last maxillary teeth abruptly 

 enlarged. 

 I. Scales in 17 rows; three labials entering the eye. 17. T. saravacensis ]>. 85. 



II. Scales in 21 rows 18. T. chrysargoides p. 86. 



III. Scales in 19 rows. 



a. Two labials entering the eye; anal entire. 19. T. flavifrons p. 87. 



b. Three labials entering the eye; anal divided. 



1. A single anterior temporal. 



aa. Third to fifth labials entering the eye. 20. T. stolatus p. 87. 

 ^/'. Fourth to sixth labials entering the eye 21. T. viltatus p. 88. 



2. Two anterior temporals. 



t Internasals shorter than praefrontals; 



scales of outer row smooth 22. T. stibminiattis p. 89. 



ff Internasals as long as praefrontals; all 

 the scales strongly keeled. 



1. Subcaudals 56 — 94; eye large. ... 23. T. chrysargus p. 89. 



2. Subcaudals 95 — 117; eye very large. 24. T. maailatus p. 90. 



I. Tropidonotus piscator (Schn.). 



Hydrtts piscator^ Schneider, Hist. Amph. I 1799, p. 247. 



Tropidonotus piscator^ Boulenger, Cat. Sn. I 1893, p. 230 (s. syn.). 



Natrix piscator, Barbour, Mem. Mus. Comp. Zool. Harv. Coll. XLIV 191 2, p. 109. 



Eye shorter than its distance from the nostril; latter turned 

 upwards; rostral visible from above; internasals narrowed in 

 front, as long as the praefrontals; frontal longer than its distance 

 from the end of the snout, as long as the parietals or shorter; 

 loreal about as long as deep; one prac- and three sometimes 

 four postoculars; temporals 2 + 2 or 2 + 3 (1+2); nine upper 

 labials, fourth 01 fourth and fifth entering the eye; five lower 

 labials in contact with the anterior chin-shields; latter shorter 

 than the posterior. Scales keeled, of two or three outer rows 



