604 Bulletin 47, United- States National Museum, 



Pectorals well developed ; ventrals very small. Humeral arch and pubic 

 bones prolonged into flat pointed processes, which project in the median 

 line of the belly ; a series of imbricated scales from the humeral bone to 

 the pubic spine, forming a ventral serrature. Dorsal fin short, median, 

 preceded by a serrated, osseous ridge, consisting of several neural spines 

 prolonged beyond the muscles; adipose fin rudimentary ; anal fin short ; 

 caudal forked. Gill opening very wide, the outer branchial arch extend- 

 ing forward to behind the symphysis of the lower jaw, and beset with 

 very long gill rakers ; branchiostegals 9, the arch near lower jaw and 

 parallel with it; pseudobranchise and air bladder present. Four pyloric 

 coeca. Small pelagic fishes found in most seas, coming to the surface at 

 night, descending into deep water by day. (upyvpoq, silvery ; TTE?U:KVG, 

 hatchet.) 



a. Anal rays 11; no spines along lower sides of caudal peduncle. 



6, Pectoral fin nearly reaching anal. HEMIGYMNUS, 901. 



bb. Pectoral fin reaching ventrals. OLFERSI, 902. 



901. ARGTROPELECUS HEMIGYMNUS, Cocco. 



B. 9 ; D. 7 or 8 ; A. 11 ; P. 9 ; V. 5. Depth of body equal to distance 

 between gill openings and base of caudal ; posterior corner of mandible 

 and angle of preopercle each with a small triangular spine ; tail without 

 spines; pectoral fin nearly reaching anal. Length 2 inches. (Giinther.) 

 Atlantic and Mediterranean in deep water ; occasional in the Gulf Stream, 

 off southern New England. (////<-, half ; -yv/uvbc, naked.) (Eu.) 



Argyropelecus hemigymnus, Cocco, Giorn. Sci. Sicil., fasc. 77, 146, 1829, Coast of Italy; CUVIEB 

 & VALENCIENNES, Hist. Nat. Poiss., xxn, 398, 1849; GUNTHER, Cat., v, 385, 1864; GOODE & 

 BEAN, Bull. Mus. Comp. Zool., x, No. 5, 1883, 220. 



Slernoptyx mediterraneus, Cocco, Giorn. Faro de Messina, iv, 7, 1838, Coast of Italy. 



902. ARGYROPELECUS OLFERSI (Cuvier). 



B. 9; D. 9 ; A. 11; P. 10; V. 6. Depth nearly or quite equal to distance 

 from shoulder to root of caudal ; tail as deep at base as long. Mandible 

 with a short, flat spine at its posterior corner; preopercle spine directed 

 downward ; tail without spines ; pectoral fin reaching ventrals. (Giin- 

 ther.) Open Atlantic; coast of Norway to Brazil and Cape of Good Hope, 

 occasionally taken in the Gulf Stream from the Grand Banks southward. 

 (Named for J. F. M. von Olfers, who sent specimens from Brazil to the 

 Museum of Paris.) (Eu.) 



Slernoptyx olfersi, CUVIER, Regne Animal, Ed. 2, n, 316, 1829, near Cape of Good Hope. 

 Argyropelecus durvillii, CUVIER & VALENCIENNES, Hist. Nat. Poiss., xxn, 405, 1849, open Atlantic. 

 Argyropelecus olfersi, CUVIER & VALENCIENNES, Hist. Nat. Poiss., xxn, 408, 1849; GUNTHER, Cat., 



v, 386, 1864; LILLJEBORG, Sveriges Fiskar, vi, 3, 1889. 

 Pleurothyris olfersi, LOWE, Fishes Madeira, 64, 1861. 



Family LXXXV. IDIACANTHID^E. 



Fishes eel-like in form "with spiny processes from anterior portion of 

 vertebrae projecting through the skin of the body. Pectorals absent. 

 Body naked. Dorsal fin beginning in advance of the vent." (Gill.) One 

 genus with 3 species known ; deep-sea fishes, eel-like in appearance. 



