GREATER FLYIXG FISTI. 133 



particularly at their union with the body, is exceedingly inter- 

 esting, as might be supposed from the use to which they are 

 applied. Owen remarks that the bone equivalent to the radius 

 in higher animals is of enormous size; but the description is 

 given more at length in a paper on E. volitans, by Thomas 

 Brown, in the sixty-eighth volume of the "Transactions of the 

 Royal Society," (Part the Second for the year 1778.) He says, 

 the united ends (of the rays of the pectoral fin) are grooved 

 or holloAved, to receive a ridge or protuberance of the scapula, 

 (or blade bone,) forming a joint of little motion except backward 

 and forward, allowing the fin in one case to lie close to the 

 side, and in the other to form an acute or right angle Avith 

 the body, but without being necessarily expanded; (and thus 

 the size of the fin is not a hindrance in rapid swimming.) 

 From near the backbone dowuAvard to the bottom, where it 

 ends in a point behind tlie gills, the body is strengthened on 

 each side with a flat bone; both firmly united together at the 

 place where narrowest, but as they become wider ujDward they 

 grow hollow on the side next the body; and towards the gills 

 the edge on each side is turned outward, so as to form a lodg- 

 ment for a strong muscle; and on the hindward part is the 

 articulation with the fin. Close above the joint, the bone he 

 terms the scapula is hollowed in the shape of a crescent, in 

 order to allow the passage of a tendon from a small muscle 

 which lies in its lower part next to the body of the fish. The 

 upper part of the ridge which forms the joint, and is received 

 by or articulated with a fin, is somewhat enlarged and round; 

 and over it the strong tendon, which is bound down by a liga- 

 ment, together with some fibres of the muscle lodged vmder the 

 inverted edge of the bone, is obliged to pass; and then passing 

 over the joint, becomes inserted into the root of the uppermost 

 and strongest fin-ray; and near the same place, a little way 

 beyond the joint, is also inverted the tendon which passes along 

 the semilunated part before mentioned of the scapula as over 

 a pulley. These two muscles have their action upward, but 

 in opposite directions; and thus the fin becomes expanded and 

 raised; while the lower portion of it is kept down by an 

 opposing influence on the hindmost and lower muscles of the 

 body. There are other muscles also of smaller size which 

 cause this fin to move backward and forward; and the whole 



