THE SHORE FISHES OF PERU 81 



indentation over the dermal projection on shoulder girdle in advance 

 of pectoral; branchiostegals 6, membrane of the right side folded over 

 the isthmus underneath that of the left side; scales about 45 to 55 

 in lateral series; vertebrae about 48; dorsal near middle of body, 

 with about 17 to 22 tsljs, the last ray greatly produced, filamentous; 

 anal with about the same number of rays, the last ray somewhat 

 enlarged ; ventral inserted under base of dorsal, with 8 rays. 



A single species, closely related to the Atlantic species 0. oglinum, 

 comes within the scope of the present work. 



OPISTHONEMA LIBERTATE (Gunther) 



Meleita libertatis Gunther, 1866, p. 603, La Libertad, El Salvador (original 



description, based on a specimen 2}i inches long). 

 Opisthonema libertate Meek and Hildebrand, 1923, p. 188, Panama Bay 



(synonymy; description; compared with 0. oglinum; range). 



Head 4.1; depth 2.85; D. 18; A. 20; P. 15; scales 53. 



Body moderately compressed, its greatest thickness nearly equal 

 to depth at origin of anal; caudal peduncle rather deeper than long, 

 2.6 in head; head rather compressed, its greatest thickness exceeding 

 length of snout and eye somewhat; snout moderately pointed, 4.15 

 in head; eye 4.15, with little adipose tissue; mouth rather small, 

 lower jaw slightly projecting; maxillary about three-fourths width 

 of eye, its lower margin convex, posteriorly broadly rounded, reaching 

 opposite anterior margin of pupil, 2.65 in head; mandible 2.4; gill 

 rakers long, slender, close-set, very numerous ; scales rather firm, with 

 rough margins, especially along the back, with one principal vertical 

 radius and sometimes with one or two partial ones; ventral scutes 

 only moderately strong, 18 in advance of ventrals and 18 more behind 

 them; dorsal in advance of middle of body, its origin about equidistant 

 from tip of snout and vertical from middle of base of anal, distance 

 anterior to its origin 2.2 in length, the fin somewhat elevated anteriorly, 

 its margin concave, longest rays 1.7 in head, filament of posterior ray 

 nearly reaching base of caudal; anal low, last ray somewhat enlarged, 

 its origin about equidistant from tip of ventral and base of caudal, 

 its base 1.55 in head; ventral inserted under anterior half of base of 

 dorsal; pectoral pointed, failing to reach base of ventral by nearly 

 length of snout and eye, 1.4 in head, 5.65 in length. 



Color in alcohol bluish above, scales with greenish reflections; the 

 bluish color changing to silvery somewhat above middle of side; 

 dorsal and caudal mostly dusky, the tips of the latter black; other 

 fins pale, exclusive of upper ray of pectoral which is dusky; a distinct 

 dark shoulder spot present, followed by smaller obscure dark spots, 

 not definitely in rows; no lines along the rows of scales on the back; 

 snout and tip of mandible verj^ dark. 



A single specimen 270 mm. long (205 mm. to base of caudal), taken 

 in a tramm.cl net in Sechura Bay, is included in the collection. It lost 



