NORTHERN CHIMvERA. 
1081 
more immediate continuation of the lateral line proper 
consists of a suborbital branch", running obliquely 
downwards and forwards along the posterior margin of 
each orbit and thence obliquely upwards and forwards 
along the suborbital margin, to a point about twice as 
far from the tip of the snout as from the eye, where it 
forms an ^-shaped curve, first downwards and back- 
wards 6 , then downwards and forwards, afterwards join- 
ing the supraorbital branch, just before the junction of 
the latter with the corresponding canal on the other side 
of the body. Where the suborbital branch first alters 
its course, on the cheek, below the lower posterior cor- 
ner of the orbit, it sends out a branch downwards and 
backwards, an opercular canal c , which becomes narrower 
and narrower until it disappears externally, being con- 
tinued, however, by a row of narrow, transversely set, 
sharp-edged pores, right across the branchiostegal mem- 
brane. Just before the origin of the opercular branch 
from the suborbital, the latter sends out another branch 
in a downward direction, a malar canal' 6 , which soon 
forks into a maxillary 6 and a mandibular-' canal. The 
former runs along the cheek, below the middle thereof, 
to a line with the anterior margin of the nostril, where 
it divides into two branches, an upper anterior (maxillo- 
rostraF) and a lower posterior (maxillo-nasal 6 ). Each 
of the last-mentioned canals crosses the under surface of 
the snout to meet and join the corresponding canal on 
the opposite side of the body; but the maxillo-rostral 
branch also sends out, upwards and forwards, in the 
median line of this under surface, an unpaired canal 1 , 
which unites it to the above-mentioned junction between 
the supraorbital branches. The mandibular branch cross- 
es over behind the lower jaw in the same manner as 
the opercular branch across the isthmus. All these ra- 
mifications- of the canals belonging to the system of the 
lateral line mark the head and in particular the snout 
with an extremely singular design, all the more striking 
as their anterior parts, on the cheeks and snout, become 
coarser, with more distinct fissure, and at certain points 
are widened and deepened, thus acquiring a moniliform 
appearance. Between the dilatations the inside of the 
canal is pierced by the inward ramifications of the caecal 
ducts described by Costa'. In addition to these canals 
appertaining to the true system of the lateral line the 
snout is furnished with the numerous muciferous sacs 
(ampullae) described by LeydigC From the many pores 
that partly follow, in single rows, the above-mentioned 
canals and the sharp fold which the skin forms in a 
curve just before the nostrils and above the lateral por- 
tion of the upper lip, partly are scattered, in groups or 
more isolated positions, between the said canals, these 
long ampullae take their origin, in the form of ducts 
directed upwards and forwards (as they approach the 
very tip of the snout, backwards). The posterior am- 
pullae' terminate carnally under the skin, between it and 
the large fibrous capsule, filed with a gelatinous mass, 
that occupies the interior of the snout, resting on the 
cartilaginous rods which we have observed above in the 
rostral region of the Holocephali. The anterior ampulhe 
on the under surface of the snout, as well as the above- 
mentioned ducts issuing from the anterior parts of the 
branches of the lateral line, penetrate within the said 
capsule. In the gelatinous mass are also embedded the* * 
large and numerous ramifications of the fifth pair of 
cranial nerves', which innervate the ampullae. The 
skin itself is marked on the back of the snout with 
a network (thimble-like pattern) of pits, and within 
each of these may be seen in miniature the same 
rotiform figure as we remarked above in the dermal 
covering that invests the muciferous sacs of the Stur- 
geons. 
The mouth is comparatively small. It presents, in 
combination with the large preoral nostrils, an appearance 
seldom exemplified in the preceding fishes. The dermal 
fold which bounds in front both the mouth and the 
nostrils has a, great resemblance, it is true, to the lower 
° Orbital and suborbital canals , according to Garman. 
b In Plate XL VI, fig. 3 of the present work there is an error, this branch being connected with the supraorbital canal. 
c Jugular canal , according to Garman. 
d Sometimes the opercular and malar branches issue in a common canal ( orbitonasal , according to Garman) from the suborbital branch. 
e Angular canal , according to Garman. 
f Oral canal , ,, ,, ,, 
3 Subrostral canal, ,, ,, ,, 
h Nasal canal, „ ,, ,, 
* Median canal, ,, ,, ,, 
3 Fna Regn. Nap., Pesci, Chimceroidei, tav. VII, figs. 1—4. 
k Arch. Anat., Physiol. 1851, p. 253, taf. X, fig. 1. 
1 According to Ewart, to whose investigations we shall return below, the nerves which innervate both the ampullae and the other parts 
of the cephalic system of the lateral line are homologous with an anterior division of the nervus facialis of the higher vertebrates. 
