604 Bulletin 4j, United States National Museum. 



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

 boues prolonged into Hat pointed processes, which project in the median 

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

 the pubic spiue, 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; pseudobranchi;e and air bladder present. Four pyloric 

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

 night, descending into deep water by day. {ap-yvpor, silvery; Trt/e/cvf, 

 hatchet.) 

 a. Aual rays 11; nospines along lower sides of ciuiilal peduncle. 



b. Pectoral fin nearly reaching aual. hf.migymnus, 901. 



lb. Pectoral fin reaching ventrals. olfersi, 902. 



901. ARGYROPELECUS HEMIGTMNUS, 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. (7)//^-, half ; -yi'^i'of, naked.) (Eu.) 



Argyropeleats hemlgymnns, Cocco, Giorn. Sci. Sicil., fasc. 77, 14G, 1829, Coast of Italy; Cuvier 

 & Valenciennes, Hist. Nat. Poiss., xxii, 398, 1849; GOnther, Cat., v, 385, 18G4; Goode & 

 Bean, Bull. Mus. Comp. Z06I., x, No. 5, 1883, 220. 



Btemoptyx viediterraneus, Cocco, Giorn. Faro de Messina, iv, 7, 1838, Coast of Italy. 



i)02. 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 Hojje, 

 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.) 



Slernoplyx olfersi, Cuvier, Regne Animal, Ed. 2, ii, 316, 1829, near Cape of Good Hope. 

 Argyropelerus cbiri-iUii, Cuvier & Valenciennes, Hist. Nat. Poiss., xxil, 405, 1849, open Atlantic. 

 Argijropelectis olfersi, Cuvier & Valenciennes, Hist. Nat. Poiss., xxii, 408, 1849; GOnther, Cat., 



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

 Pleurulhyris olfersi, Lowe, Fishes Madeira, 64, 1861. 



Family LXXXV. IDIACANTHIDiE. 



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

 vertebrie 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. 



