OR OSSEOUS SYSTEM. 6'/ 



the whole of the internal ear. From each side of the head 

 there passes down a short, round, moveable piece (,) in the 

 situation of the tympanic bone, which supports the lower 

 jaw (d,) and the moveable, free upper jaw (c,) both covered 

 closely with small teeth, like mosaic work. The scapular 

 arch (/,) is fixed to the anterior, thick, anchylosed portion 

 (e,) of the vertebral column, and the bones of the arms 

 are also anchylosed together, and to this scapular arch. 

 This fish lies at the bottom without an air-bag ; its motions 

 therefore in swimming being chiefly vertical, its hands (g, g,) 

 are very large, and extended nearly round the whole trunk, 

 from the point of the nose to the pelvic arch (h.} In the 

 large hands of the rays and sharks, there are not only very 

 numerous fingers or rays, but each finger (g,) is divided into 

 a variable number of short, cylindrical phalanges, slightly 

 dilated at their points of contact. The pelvic arch (h,) is 

 generally very perfect in the plagiostome chondropterygii, 

 and presents the rudiments of the three ordinary con- 

 stituent bones, the ilium, the ischium, and the pubis, on 

 each side ; the two pubic bones united form a band passing 

 transversely before the anus, the iliac bones ascend taper- 

 ing to near the sides of the column, and the ischium on 

 each side passes backwards. The feet are less than the 

 hands, and consist of toes (i, i,) which are shorter, less 

 numerous, and less divided than the fingers, ( g. ) The 

 great size of the hand is the more required in the rays, 

 from the smallness of the tail (&,) rendering it almost use- 

 less as an organ of motion. In the sword-fish, and in the 

 saw-fish, the upper jaw bones, the vomer, and the nasal 

 bones form a long projecting weapon of offence extending 

 from the face above the free intermaxillaries, which bound 

 the upper part of the mouth. The orbits are prolonged 

 laterally to a great distance in the zycena, or hammer-headed 

 shark, so as to give a pedunculated appearance to the eyes. 

 From the softness of the skeleton in the cartilaginous fishes, 

 the mouth, and especially the lower jaw, is very short, and 

 often extended much transversely ; and for the same reason, 

 these animals have numerous rows o'f teeth prepared to 

 supply the places of those which are successively lost, as 

 in the sharks, or have their jaws covered, as in the rays, with 

 a continuous compact layer of small permanent teeth. 



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