3o8 Field Museum of Natural History — Zoology, Vol. X. 



"Head 7.25 (old individuals) to 11 (young individuals) ; depth 8.5 

 to 14 in length to end of the anal; anal rays 200 to 260. 



"Snout 2.5 to 3; interorbital 2.25 to 3 in head; eye 4 (young) to 7 in 

 the snout, 4.25 to 6 in the interorbital, 10 to 6 in the head. 



"Body cylindrical; head depressed; width of head 1.25 to 1.6, depth 

 of head at base of the occipital process 1.3 to 1.8 in the greatest depth; 

 anus near the vertical from a point the length of the snout behind the 

 eye; dorsal profile almost straight; ventral profile slightly convex. 



"Snout very slightly pointed in young specimens, blunt in adults; 

 mouth rather large; gape straight, reaching about two-thirds of the 

 distance to almost below the eye; upper jaw included; caudal peduncle 

 one-half the length of the snout or less; pectorals 2.25 to 3 in the head; 

 origin of the anal behind pectorals, on the vertical from a point about 

 1.5 times the snout behind the head. 



"Ground-color of alcoholic specimens varies from a light slate-gray 

 in young specimens to a light orange in adults; a series of transverse 

 white stripes crossing the body in young individuals, which widen and 

 become yellow with age so that the adults are yellow, barred with black; 

 dorsal parts washed with a dark chocolate-brown containing numerous 

 black spots; fins translucent, mottled with black or brown. 



"In life the body is translucent, flesh color or pale yellow, vary- 

 ing to a distinct pink in the parts rich in blood. The stripes and 

 markings are blue or green, giving the fish a piurplish or olive-green 

 cast. This color may be deepened or lightened slightly by the ex- 

 pansion and contraction of chromatophores. 



"The general marking of the species varies considerably, specimens 

 from clear water being darker and more striped than those from muddy 

 water. Some specimens from Guatemala and from the Upper Paraguay 

 are almost without markings." (Ellis) 



This species was not taken in Panama, but it is here included because 

 it has been recorded from Central and South America, thus coming 

 within the range of the present work. 



Habitat: Guatemala south to the Rio de la Plata, and the West 

 Indies. 



34. Genus Sternopygus Muller & Troschel. 



Sternopygus Muller & Troschel, Horae Ichthyol., Ill, 1849, 13 (type 



Gymnotus macrurus Block & Schneider). 



Differing from all other Gymnotids in the free orbital margin. Body 

 elongate, compressed; head moderate; snout short; jaws equal, or the 

 upper a little in advance of the lower, the latter included at sides; teeth 

 minute, in 2 more or less distinct patches in upper jaw, in a single patch 



