224 ME. W. K. PAEKER ON THE STEUCTUEE AND DEVELOPMENT 



" stylohyal " (" interhyal "} of the Teleostei ; but it has stopped in its metamorphosis 

 at that point where, in the osseous fish, there are two subequal hyoid arches (" Salmon's 

 Skull," Third Stage, pi. 2. figs. 6 & 7, hm, c.h). In the Teleostean the ligament would 

 be more than halfway down the side of the hyomandibular {three fourths in the 

 Salmon, ibid. pi. 6. figs. 1, 2 (hm,st.h). Also in the osseous fish, a nodule of cartilage 

 appears in the ligament, like a rudimentary meniscus, which grows into a terete rod and 

 ossifies (ibid. st.h). 



The small epihyal (e.hi/) is not only attached by its apex to the hyomandibular, but 

 also it is closely tied to the front of the first epibranchial at its upper third ; this gill- 

 bearing bar is succeeded below by a ceratohyal of equal size (c.hi/) ; and then there is 

 below it a small styloid hypohyal (hJii/), situated on the notched proximal end of the 

 first hypobranchial (h.br 1). 



At first sight it would seem as though the hyoid had formed a commisural band 

 across behind the mandible (PI. XLI. fig. 4, h.br 1) ; but that is the belt formed by 

 the fusion of the first hypobranchials. The normal direction of the pharyngo-branchials 

 (p.br) is backward ; that of the fourth is continuous with the epihyal of the fifth, as 

 there is no separate pharyngo-branchial in the last arch. 



The epi- and ceratobranchials are tolerably stout, flat within, grooved outside, and 

 strongly tied together by fibrous bands. The arches end below in flat, kidney-shaped, 

 adze-shaped, and even flabelliform hypobranchials (h.br). That of the last coalesces in 

 some degree with its fellow ; and the notched and split plate thus formed reaches by its 

 fore horns nearly to the hypobranchial girder of the first arch. 



About twelve or thirteen branchial rays are attached to the hinder edge of each arch 

 (see PI. XLI. fig. 5, br.r, for those on the hyoid). These are pedate at their distal ends, 

 which lie in the outer wall of the sac ; and in some of the larger Skates their extremities 

 are very large and lobate. 



It is impossible, in the Skate, to prove that the whole of the trabecular growth is not 

 axial. Attached to the nasal sac of each side is a large, solid, short, rib-like antorbital 

 (a.o), evidently a prseoral visceral bar. 



The " labials " are the only " extraviscerals " found by me in this type. There are 

 four on each side ; and the fourth is but slightly connected with the pterygo-quadrate bar 

 (PI. XLII. fig. 4, I. 4). 



The first pair (l. 1) are lanceolate and notched in front; they help the " cutwater" 

 or " rostrum " very little, being carried away far from the nasal sacs, on which they are 

 mounted behind in the Shark (PL XXXVII. fig. 2, 1 1). The second labial {I 2) is in 

 front of the nasal opening ; the thu-d {1 3) outside ; the fourth ^ (Z 4) is articulated to the 

 second, and lies inside below the rim of the cup and the fore edge of the pterygoid bar. 



' This fourth labial of the Skate does not answer to the fourth of the Dog-fish, but to the imiei- of the two 

 on the i)terygo-quadrate of Scymnm, Sgmtina, and Gentropliorus (Gegenbaur, pis. 11 & 12, Z.: the next is 

 marked L'. 



