SKULL — TELEOSTS I09 



Weberian apparatus (a series of ossicles developed from the vertebras 

 and connected with the air-bladder) with the ear. In some of the 

 higher Teleosts the exoccipital has a process for articulation with the 

 first vertebra. The basioccipital is usually opisthocoele, bears no 

 condyle, the cavity being occupied by remains of the notochord. In 

 several Symbranchs it receives the conical centrum of the first verte- 

 bra, and in Fistularia the bone has a true condyle. 



The sphenoid cartilage rarely ossifies in the middle hne, there 

 being a parasphenoid ventral to the cartilage and, at least in some 

 genera, a suprasphenoid (membrane bone) inside the cranial wall 

 and dorsal to it. The ahsphenoids (alae temporales) he between the 

 orbit and the exit of the fifth and seventh ^^"^^^^^--^ 



nerves. They may be widely separated below y^jO'^^^ 

 by parasphenoid and suprasphenoid, or may {l^-^..^fA^^~~'^^ 

 meet dorsal to the latter. They may share in j/| ^¥S ^° Cll 

 the cranial wall, or a process from the frontal ^"^''(^^!^«/^^^"""^^ 

 may meet one from the parasphenoid, excluding ^^?^ 



the alisphenoid from the wall. They are 'Ol;^ 



reduced in tropibasic skulls, and in some cases 



. . Fig. 115. — Base of cra- 



[e.g., Cypnnus) they afford attachment to a niumof Carp (Zittei, '87). 

 part of' the hyomandibula. Orbitosphenoids "' f°^ .^Qf fi ^orta; bo, 



" -^ '^ _ . basioccipital; co, exoccip- 



are absent from tropibasic skulls, the Berycoids, itai; e^, epiotic; /, fora- 



„ , ,- , . 1 T7- 7'^ i J men magnum; so, supra- 



Regalecus, Lampris and Velifer excepted, occipital; x, foramen for 

 In platybasic crania they arise as paired connexion of Weberian 



■'■ IT apparatus with ear. 



bones which often fuse in the middle line, 



the orbital foramen lying between them and the ectethmoids. 



A large part of the mesethmoid region persists as cartilage, but 

 its dorsal surface is covered by a dermal supraethmoid which some- 

 times persists as a distinct bone, but usually fuses with the under- 

 lying mesethmoid ossification. The ectethmoid of either side, which 

 hes in front of the orbit, ossifies as an ectethmoid bone, always 

 covered by a prefrontal of dermal origin, the compound bone being 

 called by either name (also pleurethmoid). It forms the anterior 

 wall of the orbit and in most Teleosts the nasal cavity extends into 

 it, the olfactory nerve either perforating it or running between it 

 and the mesethmoid. 



The otic capsule has more bones developed in and on its wall than 

 occur in other classes of Vertebrates, some being compound bones, 

 the parts so intimately associated that the lens or even ontogeny is 



