. On the anatomy of vertebrates. Vertebrates; Anatomy, Comparative; 1866. 344 ANATOMY OF VERTEBRATES. 228. Organ of hearing, Skate. LXA'ill, the Lepiclosiren, in wliicli, as well as in the Plagiostomes, the whole labyrinth is buried in the thick basi-lateral walls of the cranivnii. In Plagiostomes the capsule conforms more closely in size and configuration to the membranous labyi-inth; its passages and compartments are lined by a delicate perichondrium, from which filaments are detached to support the semicircular canal. The vestibule is divided in the Skate and Tope into three compartments, â
. On the anatomy of vertebrates. Vertebrates; Anatomy, Comparative; 1866. 344 ANATOMY OF VERTEBRATES. 228. Organ of hearing, Skate. LXA'ill, the Lepiclosiren, in wliicli, as well as in the Plagiostomes, the whole labyrinth is buried in the thick basi-lateral walls of the cranivnii. In Plagiostomes the capsule conforms more closely in size and configuration to the membranous labyi-inth; its passages and compartments are lined by a delicate perichondrium, from which filaments are detached to support the semicircular canal. The vestibule is divided in the Skate and Tope into three compartments, â the ' alveus communis,' fig. 228, « ; the sac, ib. b, and the cysticule, ib. c ; and it has also a small ca3cal append- age, called the ' utricule,' ib. d: the otolitic contents are like soft chalk, and are dis- posed in two masses ; one very large, occu- pying the sac and the cysticule, the other small, and lodged in the utricule. A canal extends in Sharks from tlie vestibular capsule to a foramen at the upper part of the occiput, which is closed by the skin. In the Pays, besides this ' fenestra capsula3,' ib. v, a membranous canal, ib. o, p, is pro- duced from the vestibule itself, and, as Hunter well describes, ' from the union of the two perpendicular canals, fig. 228, p; which is the case with all the Ray kind, the external orifice ])eing small, and placed on the upper flat surface of the head.' So minute and approximated are these ' outer ears,'' that Scarpa may be pardoned for overlooking them, though scarcely for the warmth with which he repudiates their existence.^ The 'â 'meatus vestibuli' is provided at its bent extremity, fig. 228, o, witli a special muscle, ib. u\ A true tympanic cavity and membrane, together with a cochlea, are absent in all Fishes. But in many osseous sjiecies a com- munication is established, either by tubular prolongations, or by chains of ossicles, between the acoustic labyrinth and the air- bladder. Weber^ discovered the latter interest
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