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 Pihinochimaera rests on the frontal crest, about midway from the 

 orbital to the narial section, and has a more robust development than on any 

 other 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- 

 rhvnchus 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 ninnbers 

 and positions, but vary greatly in size. They have been worked out in Chi- 

 maera and Callorhynchus by ^lidler. 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 monsti'osa, Plate 11, said to be absent by 

 Miiller. 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 JMiiller, in Callorhynchus is no doubt connected 

 with feeding habits which necessitate grubbing or picking food off the rocks or 

 out of the sands. 



