36 DEEP SEA FISHES. 
above the hindmost tooth in the latter, or over the junction of the labials, 
the outer end of the upper jaw appears as a short horizontal bar. Above 
the end of the upper jaw and forward of the inward process of the lower, 
fiz. 4, there is a small subquadrangular spiracular cartilage. Behind each 
half of the lower jaw, in fig. 4, Plate II., behind the end of the broadened 
lower labial, there is an unnamed subcrescentic, very thin, apron-like 
cartilage, strongly invested in ligamentary tissue, underlying the ends of 
ceratohyal and basihyal. Rudiments of these cartilages are to be seen in 
the same positions on Scymnorhinus licha, where apparently they are in 
process of acquisition. 
The basihyal is wide and strong, and is deeply excavated on its lower 
surface for the ends of the ceratohyals, which it overlaps considerably. Be- 
hind this arch the branchihyal skeleton is decidedly feeble, Plate II., figs. 6, 
7. In the specimen at hand the basibranchials appear to be obsolete, unless, 
perhaps, exception is to be made for a couple of short longitudinal bars of 
cartilage lying between the ends of the hindmost branchihyals but not in 
contact with them. The lower ends of the ceratobranchials taper to points 
that are neither in contact with one another nor with the basihyal; the an- 
terior ceratobranchial is short and does not extend down as far as either of 
the others. Below the ceratobranchials the extrabranchials form an irregu- 
lar sheet of cartilage as thin as paper, Plate IL. fig. 6. In figure 7 a dorsal 
view of the branchial skeleton of the right side is given, the forward por- 
tion being turned to the left. The segmentation of the second and third 
pharyngobranchials in this figure is no doubt accidental, as also is the divi- 
sion between the hindmost two of the arches, where the epibranchials should 
be so united with and by the pharyngobranchials as to be a continuous 
cartilage. 
A specimen of Scymnorhinus licha dissected for comparison with Isistius 
differs slightly from that figured by Gegenbaur, especially in regard to the 
branchial cartilages. It has three distinct basibranchials behind the basi- 
hyal, the second of which is like the first in shape and attachments and in 
being without the division near the middle as seen in the mentioned figure 
(Das Kopfskelet, Plate XIX., fig. 2). In this specimen the pair of basihyals 
immediately in front of the hindmost: basibranchial are in contact on the 
median line and separate that basibranchial from the one next in front of it. 
in Ge- 
m"oyy 
There is, in fact, no trace of the small median plate marked “ C’ 
genbaur’s figure. 
