. On the anatomy of vertebrates [electronic resource] . als it is proportionallylarger than in true lemurs, bearing relation to the great develop-ment of the outer ears. These are large in all Lemiiridcs: thetragus and antitragus are well marked in Stenops, but instead ofanthelix there are two prominent and subparallel plates. Thevestibule is shorter, and the cochlea closer to the semicircularcanals in the Aye-aye than in Man. In the Lemuridce the com-mencement of the cochlea is wide, and its axis is parallel with aline drawn from the fore end of the ampulla of the upper semi- 230 ANATOMY OF V
. On the anatomy of vertebrates [electronic resource] . als it is proportionallylarger than in true lemurs, bearing relation to the great develop-ment of the outer ears. These are large in all Lemiiridcs: thetragus and antitragus are well marked in Stenops, but instead ofanthelix there are two prominent and subparallel plates. Thevestibule is shorter, and the cochlea closer to the semicircularcanals in the Aye-aye than in Man. In the Lemuridce the com-mencement of the cochlea is wide, and its axis is parallel with aline drawn from the fore end of the ampulla of the upper semi- 230 ANATOMY OF VERTEBRATES. circular canal, and meeting the latter just before its junctionwith the hinder semicircular canal. The stapes in lemurs is amore equilateral triangle, and the perforation is less than inmonkeys : the incus has a longer and larger body in proportionto its crura: the malleus has a shorter process, fig. 177, A. In Cebidce, ib. B, the stapes gains in length, but not much invacuity: the crura of the incus are still short, and the extensions 177. Lemur. Cebus. Cercopithecus. Homo. Otosteals, Quadrumana and Man. of the malleus are short in proportion to the mass articulatingwith the incus. The tympanum is large; the external meatusshort and very wide. In catarrhine monkeys, ib. c (Cercopi-thecus sabcBus) and in apes a nearer approach is made to theproportions and shapes of the human otosteals. There is a wider range of diversity in the external ear than inthe more essential parts of the organ. In the nocturnal Aye-aye,in which the conch is relatively largest, there is a beginning ofthe helix above the meatal fossa, but the rest of the margin isthin and unfolded: the tragus is not very prominent, the anti-tragus is better marked : a low fold represents the 6 lower crus of the anthelix, the upper one and the rest of that fold arewanting. It is only in the orangs and chimpanzees that theparts defined in the human auricle are represented. The freemargin is reflected to form a
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