THE SKATE. 37 



there are altogether four, in connection with the ventral 

 region of each olfactory capsule : the first {lb. i) supports 

 the corresponding flap of the fronto-nasal process (§ 64), the 

 second (lb. 2) lies in the fold of skin external to the naso- 

 buccal groove (§ 64), the third {lb. 3) bounds the nostril 

 internally, and the fourth (lb. 4) externally. 



35. The antorbital (palatine) cartilage (Fig. 10, 

 ant), a thick rod, attached to the outer face of the olfactory 

 capsule, and curving outwards and backwards to join the 

 anterior prolongation of the pectoral fin. 



36. The hyomandibular (Fig. 10, h.m), a club-shaped 

 cartilage, articulating by its broad end with the infero- 

 external region of the auditory capsule, and passing down- 

 wards and forwards. 



37. The spiracular cartilage (meta-pterygoid) (Fig. 

 10, sp), a semi-lunar plate, attached by ligaments above to 

 the auditory capsule and below to the inferior end of the 

 hyomandibular. 



38. The upper jaw (Fig. 10, pt.qti), formed by the 

 fibrous union in the middle line of the two pterygo- 

 quadrate cartilages, which together form a strong, 

 curved, transverse bar, connected at its extremities by 

 ligaments to the hyomandibular and spiracular cartilages. 

 Each end presents a smooth convex facet for articulation 

 with the lower jaw. 



39. The lower jaw or mandible (Fig. 10, mck), 

 formed by the fibrous union in the middle line of the two 

 Meckel's cartilages ; it closely resembles the upper jaw 

 in shape, and is articulated to it at its extremities. Both 

 upper and lower jaws are more strongly calcified than the 

 rest of the skull. 



40. The hyoid arch (Fig. 10, e.hy, c.hy, h.hy), a slender 

 rod of cartilage, attached dorsally to the postero -superior 



