SKULL — ELASMOBRANCHS 



89 



small epi- and pharyngohyals, dorsal to the ceratohyal. The inter- 

 orbital septum is membranous and the brain cavity is restricted to 

 the postorbital part of the cranium. There are no fontanelles. The 



Fig. 92. — Chondrocranium of embryo Callorhynchus (Schauinsland, '03). c, 

 ceratobranchials; ck, ceratohyoid; e, epibranchial; eh, epihyal; m, Meckel's cartilage; 

 n, nasal capsule; p, pharyngobranchial; pq, pterygoquadrate (uncertain if posterior 

 part be such); r, rostral cartilages; V-X, nerve exits. 



otic capsules open widely to the cranial cavity and the skull is mov- 

 ably articulated to the spinal column by an occipital condyle. 



Fig. 93. — Skull of Chlamydoselachus (AUis, '2^)- al, anterior labial; ao, antorbital; 

 ch, ceratohyal; ep, ectethmoid process; hm, hyomandibula; I, ligaments; m, mandible; 

 n, narial cartilage; op, optic pedicel; po, postorbital process; pi, posterior labial; 

 palatal process of pq, pterygoquadrate. 



PP. 



Some other features of Elasmobranch skulls are assembled here. 

 A few genera (Chlamydoselachus, fig. 93, Centrohatis, etc.) have the 

 rostrum reduced so that the mouth is nearly terminal. The former 



