594 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 112 



Genus Argyropelecus Cocco 



Argyropelecus Cocco, Giorn. Sci. Lett. Arti Sicilia, vol. 26, No. 77, p. 46, 1829 



(type species Argyropelecus hemigymnus Cocco). 

 Sternopty chides Ogilby, Proc. Linn. Soc. New South Wales, ser. 2, vol. 3, p. 1313, 



1888 (type species Sternoplychides amabilis Ogilby). 

 Pleurothyris Lowe, A history of the fishes of Madeira . . . , vol. 1, p. 64, 1843 



(type species Stemoptyx olfersi Cuvier). 



I consider the following unidentifiable: 



Argyropelecus bocagei Osorio, Mem. Mus. Bocage, Lisbon, fasc. 1, p. 27, 

 pi. 2, fig. 3, 1909 (type locality near Setubal) .—Seabra, Bull. Soc. 

 Portugaise Sci. Nat., vol. 5, fasc. 3, p. 176, 1911 (Setubal). — Nobre, 

 Fauna marinha de Portugal, vertebrados, vol. 1, pt. 3, Peixes 

 de Portugal, p. 350, 1935 (Setubal). 



Argyropelecus elongatus Esmark, Forh. Vid. Selsk. Christiana 1870, p. 

 489, 1871. 



Species referable to the genus Argyropelecus have the following 

 characters in common: 



Abdominal vertebrae 1 1 ; caudal vertebrae 23 to 29 ; branched caudal 

 fin rays 9+8; pectoral rays 9 to 12; dorsal 8 to 10; anal 6 to 8+5 or 6; 

 gill rakers on first gill arch 7 to 11+8 to 14 totaling 15 to 25. 



The number of organs in groups of photophores are as follows: 



Abdominal 12; anal 6; branchiostegal 6; isthmus 6; preanal 4; 

 preopercular 1 ; preorbital 1 ; postorbital 1 ; subcaudal 4 ; subopercular 

 1; supra-abdominal 6; suprapectoral 2; for location of groups of 

 photophores see figure 1 , p. 588. On the maxillary the dentition is char- 

 acteristic because on the anterior part of that bone the teeth point 

 posteriorly, and on its posterior part the teeth point anteriorly. 

 The number of teeth pointing forward and aft is variable (see table 

 2, p. 592), the number appearing to increase slightly with increase in 

 size. 



Certain species, such as aculcatus, when sexual maturity is reached, 

 develop spines around the subcaudal photophores and in front of them, 

 between the divided anal fin, around the anus, on the dorsal blade, 

 and on the ridges of the head. Both males and females may develop 

 these spines. 



The various species may be distinguished on the basis of counts of 

 fins rays, gill rakers, and vertebrae and distribution and location of 

 groups of photophores. In addition, the characteristics of the post- 

 abdominal and preopercular spines are of utmost importance in the 

 recognition of species and groups of species. 



An important feature of the genus is the dorsal blade, which con- 

 sists not of dorsal spines or rays but of more or less fused 

 pterygiophores, the dorsal rays having been lost. Radiographs 



