424 . PHILOSOPHICAL TRANSACTIONS. [aNNO 1778. 



pushed out of their sockets, which the fish is capable of doing considerably, 

 their sphere of vision is greatly increased. The skin is uncommonly firm for 

 the size of the animal, and the scales large and thick. As they have no mem- 

 brane to shade the eye, they are not able to cover the pupil in any of its motions. 

 The wing is no other than a large pectoral fin, composed of 7 or 8 ribs or 

 pinions, the largest of which, being uppermost, reaches almost to the tail ; the 

 rest, gradually shortening to the bottom, are connected by thin membranous 

 pellucid films or webs from their roots, which spring near the gills to the very 

 summit, where they lose themselves in slender points : at their thickest ends, 

 approaching each other, they unite in a line, which, in correspondence with the 

 form of the gills, is nearly the segment of a circle ; though they are there con- 

 nected, it is in such a manner as to allow of being drawn a little asunder, which 

 separation is considerable at the other extremity. The united ends are grooved 

 or hollowed, to receive a ridge or protuberance of the scapula, forming a joint 

 capable of little motion, excepting backward and forward ; in the one case the 

 wing lies close to the side ; in the other, it is moved from the side forward, 

 forming an acute or right angle with the body of the fish ; but neither at this 

 time expanded. These two motions are performed, I presume, in common 

 swimming. 



The fore part of its body, from near the back bone downward to the bottom, 

 where it terminates in a point, is fortified just behind the gills by a flat bone on 

 each side, which answer all the purposes both of clavicles and scapulae in land 

 animals : they are firmly united before, or at the inferior part where they are 

 narrower, and running upward, widening as they approach the back, they 

 become somewhat hollow towards the body, and a little convex outwardly at the 

 broadest part; but towards the gills the edge of the bone on each side is turned 

 outward, like the cape of a garment, to form a smooth surface for them, and at 

 the same time to give lodgement to a strong muscle under it, which fills the 

 whole space, on the superior part of the bone ; for on its posterior part the 

 articulation is made with the wing. 



Just above the point the scapula is smooth and hollowed, in the manner of a 

 crescent, to allow a tendon to pass from a small muscle which lies on the inferior 

 part of it, next to the body of the fish. The upper part of the ridge that forms 

 the joint, and is received by, or articulated with the wing, is rounded and some- 

 what enlarged, over which the strong tendon, bound down by a ligament, to- 

 gether with some fibres of the muscle lodged under the inverted edge of the 

 bone, is obliged to pass, and, going over the joint, is inserted into the root of 

 the strongest and uppermost pinion ; near to which place, the tendon, passing 

 in the semi-lunated part of the scapula beforementioned, as over a pulley, is also 

 inserted a little way beyond the joint. By the action of tliese two muscles. 



