316 Fretp Museum or Naturat History — Zodétocy, Vo. X. 
54. Gambusia nicaraguensis Giinther. 
Gambusia nicaraguensis Gianther, Cat. Fish. Brit. Mus., VI, 1866, 336, and 
Trans. Zool. Soc. London, 1868, 483, Pl. 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., Zodl. 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. roor 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. 
Fila, 4. DISTAL PART OF INTROMITTENT ORGAN OF Gambusia nicaraguensis Ganther. 
(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 
