DR. J. MURIE ON THE ANATOMY OF THE WALRUS. 437 
and rather posterior surface of the terminal bulbous portion of the auditory canal, or 
f-shaped tubular cartilage. 
The second, attrahens (atr, fig. 26), or anterior auricular, is throughout rather 
broader but very little shorter than the preceding. It arises from the tissues below 
the hinder segment of the zygomatic arch, and, with an upward and backward slant, 
terminally fixes itself to the under anterior border of the auditory coil or expansion. 
The third muscle, lying behind the last mentioned, is the shortest but by far the 
strongest. It has origin by a stoutish tendon from the upper surface of the zygoma; and, 
ascending almost vertically, its roundish fleshy belly is inserted into the inferior angle 
of the upper bend of the auditory canal and into the front of the perpendicular portion. 
The origin of this muscle is not, as in Man, from the mastoid region; nevertheless it 
corresponds most nearly with the posterior auricular or retrahens aurem (ret, fig. 26). 
As regards action, the upper muscle retracts as well as raises the meatus auditorius, 
whilst the lower pair drag the cartilaginous tube forwards and downwards. It may be, 
though, that by a combined action of the investing fascia the posterior auricular gently 
pulls the circular bulb of the meatus slightly backwards. 
It is very remarkable that such auricular muscles should be so well developed where, 
in the absence of a large expanded concha, sound is seemingly not so needful a requisite 
to be caught as in many of the land-Mammalia. Because deficient in external aural 
apparatus, the Walrus must not be supposed to be dull of hearing ; on the contrary, his 
powers in this respect are acute rather than otherwise. Perchance an enlarged pinna 
in a watery element would not render the vibrations more susceptible of impress on 
the internal acoustic apparatus; yet there can hardly be a doubt that the external 
auditory canal is betimes modified in its curvature by the said fleshy strips. In Ceta- 
ceans, ¢. g. Lagenorhynchus, where the ear-hole is extremely minute and rigid, I have 
found similar homologues of auricular muscles. 
Unlike the Otaria, the Walrus possesses a slight median tendon in the digastric 
muscle. The tendon, however, occupies only the inner side of the muscle. 
Of the short muscles on the ventral surface of the neck, all are of large size. The 
rectus anticus major springs by fleshy digitations from the diapophyses of the sixth, 
fifth, fourth, and third cervicals, and increases in thickness as it approaches its basi- 
occipital insertion. In some respects this resembles what obtains in Man. ‘The rectus 
anticus minor has origins from the diapophyses of the third and second cervical ver- 
tebre, passing forwards to the basioccipital. The longus colli may be regarded as 
consisting of two divisions. The anterior or upper portion is separated readily into 
four or more slips. These arise fleshy from the ventral surface of the bodies of the 
cervical vertebra, betwixt the seventh and second, and are inserted, partly fleshy and 
partly by tendon, into the anterior transverse processes. The second or posterior portion 
bears considerable resemblance to the condition found in Otaria, and proceeds on to the 
bodies of the anterior dorsal vertebre. 
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