135 
mouth nearly vertical, nearly reaching the vertical through the 
middle of the eye. Mandible with a prominent spine at the sym- 
physis and a short flat one at its posterior corner. One pracoper- 
cular spine directed downward. One spine at the shoulder. Ventral 
keel with a short anterior and two much stronger posterior ones, 
Fig. 49. Argyropelecus olfersi Cuv. 
which are directed down- and backward. Soft part of dorsal 
before the beginning of the second '/, of the length, ending 
before the vertical through the origin of the anal, which origin- 
ates immediately behind the anus, in the beginning of the last 
'/,. Origin of ventrals below the middle of the second '/, of 
dorsal, behind middle of length. Pectorals reaching ventrals. 
A long low adipose fin. Caudal deeply emarginate. Luminous 
organs: an antorbital below nostrils, a suborbital near posterior 
end of maxillary. Two operculars, the dorsal nearly on the 
level of the ventral margin of the eye, the inferior behind prae- 
opercular spine. A group of 6 on the branchiostegal membrane. 
In the ventral series meeting that of the other side, a group 
of 6 behind the isthmus, along the ventral edge a series of 12 
meeting those of the other side. Between ventrals and caudal, 
on each side 3 far distant groups, the first group before anal 
with 4 organs, the 2 median of which are shorter. Second group 
above the middle of the anal with 5—6 organs of unequal size, 
the middle ones of which are somewhat shorter. In the third 
group before the anterior.rays of caudal 4 nearly equal organs. 
A group of 2 organs above pectorals and a series of 6 somewhat 
distant organs between it and the ventral. Length about 100 mm. 
