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202 THE RADIATING ORGANS OF THE DEEP SEA FISHES. 
cell plates of the cephalic discs of HZ. radiatus. In H. macrochr the upper 
ends of these cells are strongly curved and pass into a superficial pellicle 
which looks as if it were composed of the upper ends of the cells them- 
selves, drawn out in a thread-like fashion and laid down tangentially. 
Macrurus canus Garman. 
Plate 5, Figs. 18-20. 
This species has been described by Garman (99, pp. 217, 364, Plates 49, 
84, Figs. 1,2). The radiating discs are situated in the floors of the cephalic 
slime canals. In surface views they appear elongate hexagonal (Plate 5, 
Figs. 19, 20). They are 2-4 mm. long, white in color and very conspicu- 
ous. The wall of the slime canal is lustrous and the part surrounding the 
discs occupied by large and richly ramified dark brown pigment cells (Migs. 
19, 20 p) so that they stand out as brilliantly white patches from a dark sur- 
rounding. On each side of the head there are 3 maxillary, 6 orbital, 2 eth- 
moidal, 16 occipitoparietal, 7 mandibular, and 6 opercular radiating dises. 
A stout nerve, the main dise nerve, (Plate 5, Figs. 19, 20 n) approaches each 
of these organs from the side and extends through its basal part towards its 
centre, where it abruptly divides into numerous paratangentially extending 
branches. ‘These discs are exceedingly tender structures, and unfortunately 
not sufficiently well preserved to allow of their minute structure being 
clearly made out. A square patch occupying the central part of the hex- 
agonal dise is much less transparent than the remainder (Figs. 19, 20), and 
it seems that the ramifications of the main disc nerve are confined to this. 
The dises here are certainly not so simple in structure as in Leucicorus and 
Bassozetus and seem to approach those of Halosaurus. They probably have 
a structure similar to that of Halosaurus. 
Ipnops agassizii Garman. 
Plate 1, Figs. 3-5. 
This species was described by Garman (’99, p. 259, Plate H, Figs. 2, 
2a). On the upper side of its dorso-ventrally compressed head a whitish ° 
patch 12 mm. long and equally broad, composed of two symmetrical halves, 
aright and a left one, is met with (Plate 1, Figs. 3-5 d). Moseley (87, pp. 269- 
276, Plates 67, 68) has found similar discs in another species of this genus, 
