252 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
Plate 10, and in the young of other Chimaeroids the facial region of the skull 
is shorter than in the adult. 
- Whether a distinct rostral prolongation is developed or not, the rostral carti- 
lages are similar in all the genera of recent Chimaeroids. The upper rostral 
cartilage of Rhinochimaera rests on the frontal crest, about midway from the 
orbital to the narial section, and has a more robust development than on any 
cther of the known Chimaeroids, Plate 1, Figure 2. On Chimaera colliei the 
point of attachment of this cartilage is about the same, but on Chimaera mon- 
strosa, Plate 11, it is higher on the forehead, and on Callorhynchus callo- 
rhynchus it is much nearer the nasal sacs. Though Plate 10 was drawn from 
a very young specimen, which had not attained the great facial prolongation of 
individuals of the same species at greater age, it shows the lower rostral carti- 
lages with a proportional development approaching that seen in Rhinochi- 
maera, Plate 1. As shown on Plate 11, in Chimaera monstrosa, and in other 
species of the same genus, the lower or subrostral cartilages are much dwarfed 
in size, as also is the case with the upper or suprarostral, though in much less 
degree. The fact that these cartilages are present and so well developed in 
the species of Chimaera, in the absence of a rostrum, suggests that a rostrum 
existed in ancestral forms and has become obsolete. The three rostral carti- 
lages are present, in varying degrees of perfection, on each genus of the 
Chimaeroids. The bases of these cartilages are attached to the skull by liga- 
ment in such a way as to admit of considerable movement of the distal ex- 
tremities up and down. On Chimaera monstrosa, Plate 11, the suprarostral 
cartilage presents the appearance of having originally been attached near the 
nasal capsules, as in Callorhynchus, and of having the basal portion, for a short 
distance, brought back against and fused with the frontal region of the skull; 
the ligamentous attachment, however, is at the base of the free portion. 
The labial cartilages, present on all the genera, are the same in numbers 
and positions, but vary greatly in size. They have been worked out in Chi- 
maera and Callorhynchus by Miiller. On Rhinochimaera the lower labial car- 
tilages — that is, the larger ones (called by Miiller the unterer unpaarer Lip- 
penknorpel in Callorhynchus, but actually paired in this genus as in the other 
genera) —are smaller than those of Callorhynchus callorhynchus, Plate 10, 
and larger than those of Chimaera monstrosa, Plate 11, said to be absent by 
Miller. By some authorities the remnants of the intermaxillaries and the 
maxillaries are to be found in the superior labial cartilages. In all of the 
genera examined there is a pair of lower labial cartilages. This pair is closely 
bound together in large specimens of species of Callorhynchus, but in young 
individuals the two are distinct, and in very young ones of Callorhynchus cal- 
lorhynchus there appears to be an additional pair of slender bars of cartilage 
crossing immediately in front of the large ones. These are distinctly shown 
on Plate 10; on later stages they have apparently fused with the larger ones 
behind them. The excessive development of the chin cartilages, the unterer 
unpaarer Lippenknorpel of Miiller, in Callorhynchus is no doubt connected 
with feeding habits which necessitate grubbing or picking food off the rocks or 
out of the sands. 
