144 BULLETIN 189, UNITED STATES NATIONAL MUSEUM 



tal part of head; head flat above, its sides vertical, with a broad 

 shallow median groove extending from about postei'ior angle of mouth 

 to opposite posterior margin of eyes; snout very long, slender, its 

 length to tip of upper jaw 4.7 in length; eye 12.3 in head, or 2.85 in 

 postorbital part of head; interorbital equal to diameter of eye; en- 

 larged teeth in jaws scarcely compressed, rather far apart; scales 

 small, not accurately countable, about 50 oblique rows under base of 

 dorsal, present on interorbital and on the gill covers; lateral line 

 directed upward immediately behind base of anal, becoming mid- 

 lateral in position and formmg a rather prominent keel on caudal 

 peduncle; dorsal only moderately elevated anteriorly, the longest rays 

 about twice diameter of eye, its origin about 1.5 times diameter of 

 eye behind origin of anal; caudal deeply lunate, the lower lobe the 

 longer, about as long as the postorbital length of head and half the 

 eye; anal larger and higher anteriorly than the dorsal, the longest 

 rays about twice diameter of eye, its base 2.2 in head; ventral short, 

 rounded, only a little more than half length of pectorals, inserted 

 nearly equidistant from anterior margin of eye and base of caudal; 

 pectoral pointed, equal to length of postorbital part of head, 4.35 

 in head. 



Color greenish above, sides silvery, pale underneath; a dark band 

 on middle of back and another one along the side; the rays and the 

 distal part of elevated portion of dorsal dark, the rest of fin pale; caudal 

 dusky; outer half of elevated part of anal dusky, the rest of fin mostly 

 pale; ventral pale; pectoral mostly pale at base, distally quite dark. 



The Mission secured a single specimen, 252 mm. (231 mm. to base 

 of caudal) long, under a light at Pachacamac Island. It is the third 

 specimen reported from Peru. I have compared this with others 

 from Panama Bay and with two from the Galapagos Islands, and 

 found them all identical. This species is characterized chiefly by the 

 short ventral fins, the rather short dorsal, the strongly depressed 

 caudal peduncle provided with a lateral keel, and the black-tipped 

 dorsal, anal, and pectoral fins. 



Range. — Gulf of California to Peru, and the Galapagos Islands. 



Family HEMIRAMPHIDAE: Halfbeaks 



Body rather elongate, more or less compressed; mandible various, 

 generally greatly produced, equal to or longer than rest of head in 

 Peruvian species; teeth short, in a band in each jaw; gill rakers de- 

 veloped, long or short; scales cycloid, often deciduous; anal fin modified 

 in viviparous species, unmodified and similar to dorsal in others; no 

 finlets; caudal round or forked, if forked the lower lobe the longer. 



Two genera, in which the mandible is greatly produced, come w^ithin 

 the scope of the present work. The standard length in the species 

 herein considered is the distance between tip of upper jaw and base of 

 caudal. 



