331 



A, Prefrontals fused; ventrals 141-154; scales 15-17; a white dot on each 



scale Trimetopon gracile (Giinther). 



This is Ahlabes gracilis Giinther 

 1872, Ann. Mag. Nat. Hist. (4), 9, 

 p. 18, pi. 3, fig. D; Cartago, Costa 

 Rica; type, Brit. Mus. Nat. Hist, 

 no. 71-11-22-19, 20. It includes 

 Trimetopon pliolepis Cope 1885, 

 Proc. Amer. Phil. Soc. 22, p. 177; 

 San Jose, Costa Rica. The British 

 Museum has it from Turrialba and 

 from La Palma. I have taken it 

 from the latter locality. 

 AA. Prefrontals fused; ventrals 122; scales 15; uniform, back of head white. 



Trimetopon simile, sp. nov. 

 AAA. Two prefrontals; ventrals 141-153; scales 15; a lateral white stripe. 



Trimetopon barbouri, sp. nov. 



Trimetopon simile, sp. nov. 



Type. — Museum of Comparative Zoology no. 15263, received from the 

 Museo Nacional de Costa Rica. 



Type locality. — Reventazon, Costa Rica ( = La Junta) . 



Description.- — Scales 15; ventrals 122; anal divided; caudals 69; prefrontals 

 fused; oculars 1-2; temporal 1-1; supralabials 7, infralabials 7; third and 

 fourth supralabials are below the eye; four infralabials are in contact with the 

 anterior chin shields which are longer than those posteriorly; black, white 

 below; head white as far forward as middle of frontal, and including third 

 labial; a black spot on seventh labial; length 155 mm., tail 50 mm. 



Trimetopon barbouri, sp. nov. 



Type.- — Museum of Comparative Zoology no. 23877. 



Type locality.- — Pedro Miguel, Canal Zone, Panama, 



Description. — Male: scales 15; ventrals 153; anal divided; caudals 58; 

 oculars 1-2; temporals 1-1; two prefrontals; two nasals; supralabials 7, 

 infralabials 8; third and fourth supralabials in contact with eye; four infrala- 

 bials in contact with anterior chin shields; darkish, light below; no light collar; 

 a stripe from eye to fifth and sixth labials; a stripe from parietal on second 

 temporal and seventh labial; a light stripe on fifth scale row and upper half 

 of fourth; first, second, and one-half of third rows lighter; length 260 mm., 

 tail 65 mm. 



Variation. — Of four from Ancon (Mus. Comp. ZooL no. 23873- 

 23876) two have ventrals 141 and 149. 



Remarks. — The genus is composed of these three obviously 

 related forms, but harhouri, with its normal prefrontals, is not 

 very remote from some of the Central American forms of Liophis 

 (Rhadinea), approaching such forms as calligaster and seper aster. 



