176 DEEP SEA FISHES. 
Over the head the mucous and luminous systems are peculiarly dis- 
tributed. In some measure their arrangement recalls that seen in the 
cephalic canals of the lateral system on certain Selachia (“On the Lateral 
Canal System of the Selachia and Holocephala,” 1888, and Plate LXX., 
below). While the structures in these cases are very different the resem- 
blances in locations are sufficiently close to permit the use of similar terms 
in description. The cephalic canals are tortuous and the fusiform disks, 
being transverse, are not as on the body vertical to the general axis, but 
are directed toward all points. On the top of the head two rostral series 
converge backward from the foremost of the glandular spindies until near 
the interorbital space where they become divergent and, as cranials, traverse 
the space to the frontal region behind it, on reaching which each branches 
to send one branch inward nearer the median line of the crown and another 
out to pass backward nearer its edge. At the back of the skull each of the 
inner branches turns outward and passing down and backward reaches the 
hindmost organ of the cephalic series on the post-temporal (scapula). In 
each of the cranial series there are eleven of the glandular bodies. From 
the outer branch of each cranial the orbital and the suborbital series, of 
seven glands, passes down behind the eye and forward below it. Farther 
back from the end of the outer cranial branch there is a short occipital 
thread without spindles connecting the outer with the inner branch, and an 
opercular series extends down on the preopercle and then continues forward, 
as the oral, under the lower jaw. No aural connection was to be traced. 
Between the cranial and the mandibular symphysis there are nine of the 
luminous disks. On each side of the head there are twenty-five of the 
glandular spindles, which with the forty on each side of the body make one 
hundred and thirty in all. It is difficult from the material at hand to deter- 
mine the connection between the series on the head and those on the body ; 
the thread connecting one gland with another disappears on the post-temporal 
and reappears again at the first spindle on the body. Whether the thread 
is continuous, as is to be expected, is still problematical. Immediately be- 
hind the head the thin scale-covered black skin extends down along the 
shoulder girdle to the abdomen. Beneath this skin above the pectoral the 
large scales appear to be isolated and each to lie at the bottom of a sac 
surrounded by membranes that are attached at the edges or between the 
scales. Bits of what may have been coagulated mucus occur in some of the 
sacs; unless they have been greatly macerated the structures are hardly 
like those of the disks in the lateral line. 
