182 THE RADIATING ORGANS OF THE DEEP SEA FISHES. 
Myctophum aurolaternatum Garman. 
Plate 5, Figs. 21-23. 
This species has been described by Garman (99, p. 254, Plate 55, Fig. 3). 
His statements concerning the distribution of the radiating organs agree with 
my observations, but his figure (99, Plate 55, Fig. 3) differs in several 
respects from what I find in the specimen examined. 
The radiating organs are for the most part nearly equal in size about 
600 » in diameter. They are provided with reflectors, lustrous, and there- 
fore, although so small in size, quite conspicuous. 
There are on each side 3 mandibular (Plate 5, Figs. 21, 22 ma), — these are 
mentioned by Garman (’99, p. 265), but not represented in his figure (’99, 
Plate 55, Fig. 3),—4 branchiostegal, 2 opercular (op),— the lower one, 
which is smaller than the upper one, is not represented in Garman’s figure 
(99, Plate 55, Fig. 3),—3 pectoral (pe) forming an are just behind the 
gill slit, 5 ventrothoracic (vt), over the last of these | anterior lateral (al), 
4 yventromedials (ve), 3 mediolaterals (ml) forming an oblique row, 10 
anterior ventroanal (va), 1 posterior lateral (pl), over the last one of the 
former 6 posterior ventroanal (vp) — according to Garman’s figure (99, 
Plate 55, Fig. 3) 7, and 2 ventrocaudal radiating organs (vc) at the base 
of the tail. 
All the organs examined appear to have the same structure. Viewed 
from the surface each appears as a lustrous spot enclosed above and at the 
sides by a dark strip, which has the shape of a horseshoe open below. 
Each radiating organ of the body lies between two scales. The outer one 
which covers it (Plate 5, Fig. 23 ss) is convex and possesses near the centre an 
II-shaped thickening (t) produced by a local accumulation of calcareous 
laminae, which make the scale very brittle. On treatment with acid the 
thickening disappears. The horseshoe-shaped pigment. stripe mentioned 
above is attached to the inner side of this scale. An axial section of the 
organ vertical to the medial plane of the fish passes through the apex of 
the horseshoe (p). The lower scale (si) is concave; on its inner side a 
continuous layer of pigment (pp) is observed. The lenticular space be- 
tween the convex outer and the concave inner scale is for the most part 
occupied by connective tissue (c). This is composed of a ground substance 
traversed by slender, elongated cells which are somewhat irregularly curved. 
