72 Field Museum of Natural History — Zoology, Vol. X. 



anal, its origin midway between base of caudal and eye; origin of anal 

 under about fourth anal ray, its free edge rounded, longest rays i.i to 

 1.2 in head; caudal peduncle deep, i.i to 1.2 in head. 



Color dark olivaceous, the center of each scale lighter, a black 

 blotch ( 9 ) about twice as large as eye above origin of anal ; color of 

 male similar except posterior half of body with 7 dark cross bars (37 mm.) 

 becoming faint in larger specimens. 



Described from several females 43 to 65 mm. The males much re- 

 semble in general form the females. Specimens 45 to 53 mm. show 

 following measurements: Head 3.9 to 4.0; depth 2.5; eye 2.7 in head; 

 snout 4.2; pectoral i.o, caudal peduncle i.o; modified anal long and 

 slender, its tip reaching base of caudal, its length .56 in head. 



Alfaro gen. nov. 



This genus belongs to the subfamily Tomeurinae * in having the 

 lower row of scales on each side with their inner surfaces together form- 

 ing a knife-like edge behind the anal fin ; the dorsal fin is wholly on the 

 posterior third of the body ; the 2 first rays of the anal are elongate and 

 modified, but less so than in other viviparous genera in this family, 

 which have the elongate anal. 



I dedicate this genus to Dr. A. Alfaro, Director of the National 

 Museimi of Costa Rica and the best known scientist of the Republic. 



Alfaro acutiventralis sp. nov. 



Type No. 7579, F. M. N. H.; length 75 mm.; Guapilis, Costa Rica. 



Head 4.2 to 4.3; depth 3.4 to 3.7; D. i, 6 or 7; A. i, 8 or 9; scales 32 

 to 34. 



Body elongate, much compressed, profile from dorsal to nape 

 straight, a slight angle at nape; top of head flat, covered with scales; 

 mouth rather large, its gape half way to eye; teeth fixed in both jaws, 

 in bands, those of the upper jaw subequal, the outer series of lower 

 jaw enlarged; lower jaw the longer; premaxillary very protractile; 

 maxillary small, its tip reaching below anterior margin of the orbit; 

 eye 2.7 to 3,1 in head; snout 2.7 to 2.8; dorsal fin posterior, its distance 

 from base of caudal about 2.3 in its distance from tip of snout; pectoral 

 broad, of 13 rays, situated on axis of body, its length 1.2 to 1.3 in head; 

 anterior rays of anal fin long, falcate, longest .9 to 1.0 in head; ventrals 

 short, its rays 6; gill rakers 17 or 18; lateral line on row of scales above 

 pectoral for 7 or 8 scales, then on the row below to base of caudal; 

 many of the scales on the posterior half of the body with a small pore, 

 peritoneum dusky, alimentary canal short; vertebrae 20-1-15 = 35. 



•Eigenmann, Mem. Car. Mus., vol. v, 460, 1912. 



