Nos. IAND2.] ANATOMY OF SCOMBER SCOMBER. 163 



The number of dermal rays in the pectoral fin varied, in the 

 different specimens examined, from seventeen to twenty. In two 

 specimens, in which there were eighteen rays, three of them artic- 

 ulated directly with the scapulare; two articulated with the an- 

 terior basal bone ; three with the next posterior bone ; one between 

 that bone and the third bone; four with the third bone; and five 

 with the fourth bone. In one specimen, in which there were 

 twenty rays, they articulated with the basal bones as shown in the 

 figures. 



The rays are all usually formed of two bones, a mesial and a 

 lateral one, but the antero-dorsal, or propterygial ray was some- 

 times formed of a single bone. The two bones, each representing 

 half a ray, are usually separated by a line of tissue which at the 

 same time binds the bones together. They are easily separated 

 one from the other. 



The mesial half of the propterygial ray (Fig. 48) has an en- 

 larged proximal end, from w^hich a stout process projects back- 

 ward, downward and mesially. This process gives insertion to 

 one of the tendons of the ventral one of the two adductor pro- 

 fundus muscles of the fin, and to a tendon that extends forward 

 and upward from the ray to the mesial surface of the dorso-pos- 

 terior process of the dorsal end of the clavicle. The anterior sur- 

 face of the proximal end of the mesial half of the ray gives inser- 

 tion to the large tendon of the levator muscle of the fin. The 

 lateral half of the ray did not, in the specimen examined, give 

 insertion to any part of the muscles of the fin. The anterior sur- 

 face of the proximal end of the entire ray is convex ; the posterior 

 surface concave. 



In the rays that follow the propterygial one, the proximal end 

 of each of the two bones that form the ray is produced backward 

 and downward as a process, the ends of the bones here spreading 

 and leaving a \'-shaped angle between them. This angle is filled 

 with tough tissue which rests upon the articular edge of the 

 primary girdle. On the lateral half-ray, near the end of its 

 produced, process-like proximal end, there is a large eminence 

 which gives insertion to two tendons, one belonging to the ab- 

 ductor superficialis muscles of the fin, and the other to the ab- 

 ductor profundus. On the mesial half-ray a similar eminence 



