io8 



CHIM^ROID FISHES AND THEIR DEVELOPMENT. 



region is wider and more compressed, the palato-quadrate is reduced and trans- 

 ferred to a more anterior position, nor is it as distinct an element as Schauinsland 

 figures it in the kindred genus. As further evidence of the more modified character 

 ol the skull of Chimsera, we observe that the preorbital ridges are curiously 

 flattened, forming together a transverse brow-plate in the young skull; and that the 



A 



Figs. 84 A-D. Reconstruction of skull of CKim&era embryo shown in plate IX, fig. 50. The model is shown in lateral, three-quarters 



dorsal, and caudal aspects. 



Ot-6, Anterior and posterior points at which the palato-quadrate element has fused with the cranium ; etc, roof of auditory capsule : ch, ceratohyal ; /". fora- 

 men through which the ophthalmic nerve passes out of the cranium ; fos, foramen through which passes the superficial branch of the ophthalmic nerve; 

 gh, basihyal ; hch, hypochordal portion of the basis cranii ; /?, hyomandibular : pb, pharyngobranchial ; p<lf, palato-quadrale fissure; pro, 

 preorbital process; pto, poslorbital process; r, median rostral cartilage; s, spiracular cleft later retained as the foramen through which the hyomandibular 

 branch of the seventh nerve passes to ihe under side of the skull ; V^- VII, foramen for fifth and seventh nerves. 



postorbital ridges are reduced in size. We note also the greater width of the 

 cranium in Chimaera and the lesser development of cartilage in the region between 

 the orbits. In short, we can justly conclude that at corresponding stages the skull 

 of Callorhynchus more closely resembles that of a young shark than does the skull 

 of a young Chimaera. The proportions in the case of Callorhynchus are distinctly 



