3i6 Field Museum of Natural History — Zoology, Vol. X. 



54. Gambusia nicaraguensis Giinther. 



Gambusia nicaraguensis Giinther, Cat. Fish. Brit. Mus., VI, 1866, 336, and 



Trans. Zool. Soc. London, 1868, 483, PI. 82, fig. 3 (Lake Nicaragua); 



Jordan & Evermann, Bull. U. S. Nat. Mus., XLVII, 1896, 682; 



Regan, Biol. Cent. Amer., Pisces, 1907, 96 (Lake Nicaragua; El 



Hule, Mexico), and Proc. Zool. Soc. London, 1913, 985, fig. 168 A 



(Lake Nicaragua; El Hule and Coaxacoalcos, Mexico). 

 Paragambusia nicaraguensis Meek, Field Col. Mus. Pub., Zool. Ser., V, 



1904, 133 (Otopa; Boca del Rio; El Hule; Obispo; Perez). 



Head 3.3 to 3.8; depth 3.3 to 3.8; D. 7 or 8; A. 10 or 11; scales 29 to 31. 



Body elongate, compressed; upper profile from snout to dorsal 

 straight or slightly convex; head rather low, flat above; snout short, 2.7 

 to 3.8 in head; eye 2.8 to 3.5; interorbital 2 to 2,9; mouth very small, 

 the gape extending only about half way to eye; teeth in jaws in villiform 

 bands; gill-rakers short, about 14 on lower limb of first arch; scales 

 moderate, cycloid, extending forward to eyes; caudal peduncle strongly 

 compressed, its least depth 1.5 to 1.8 in head; origin of dorsal in female 

 over or slightly behind base of last ray of anal, or about midway between 

 posterior margin of eye and tip of caudal, in male notably behind base of 

 last ray of anal and about midway between tip of snout and tip of caudal; 

 caudal fin rounded; anal fin in female inserted somewhat nearer tip of 

 snout than tip of caudal, its outer margin concave, in adult male it is 

 inserted about midway between tip of snout and base of caudal, the 

 longest modified ray 2.6 to 2.8 in body, the first produced ray with 

 strong serrations on distal portion and the posterior branch of second 

 and third produced rays each with a strong retrorse hook at apex; ventral 

 fins small, reaching origin of anal in female, and past origin of anal in 

 male; pectoral fins moderate, 1.5 to 1.85 in head. 



Fig. 4. Distal part of INTROMITTENT organ of Gambusia nicaraguensis Gimth^r. 



(Greatly magnified.) 



Color greenish; each scale on upper part of sides with a dark dot, 

 forming lines along the rows of scales. Dorsal and caudal with black 

 spots forming bars; other fins unmarked. 



Of this species we have over 100 specimens. The largest female is 

 45 and the largest male 27 mm. in length. Nearly all of our specimens 



