2 26 ALUS. [Vol. XVIII. 



In Scomber there is but one occipito-supraclavicular ligament, 

 and it lies in the third septum. In Ainia (No. 4, p. 708) there 

 are two of these ligaments, one l}ing in the fourth septum and 

 the other in the fifth septum. In Scomber the first two hori- 

 zontal ribs are found in these fourth and fifth septa. As these 

 two ribs in Scomber lie in, or immediately below, the horizontal 

 muscle septum, and are accordingly directed toward the lateral 

 canal of the body, they thus have the same general position 

 and direction that the two ligaments in Amia have. If 

 then the first two free vertebrae of Scomber are represented in 

 Amia by the last two occipital vertebrae (No. 6), the two asso- 

 ciated horizontal ribs, in Scomber, .would seem to be naturally rep- 

 resented, in Amia, by the occipital ligaments. The occipital liga- 

 ment of Scomber would then be another more anterior, but 

 homodynamous structure, not perceptibly differentiated in Amia. 



5. Muscles of the Pectoral Fin. 



There are, in Scomber, three lateral and three mesial muscles 

 associated with the pectoral fin. 



The largest of the lateral muscles (Abds, Figs. 45-49) lies 

 superficial to the other two, and almost completely covers them. 

 It arises from a median portion of the postero-mesial surface of 

 the antero-lateral wall of the clavicle, the surface of origin extend- 

 ing nearly the full length of the grooved part of the bone. Super- 

 ficial to the surface of origin of this muscle the same surface of 

 the clavicle gives insertion to portions of the trunk muscles, and 

 internal to it, to a portion of the fibers of a deeper muscle of the 

 fin. All of the fibers in the dorsal part of the superficial muscle 

 run directly upward and backward, in a nearly parallel course, 

 toward the base of the fin, and, becoming tendinous, and separat- 

 ing more or less completely into separate bundles, are inserted 

 on the eminences on the proximal ends of the lateral half rays of 

 the fin. In this part of the muscle there are, often, more separate 

 tendinous ends than there are dermal rays in the fin, two tendons, 

 or parts of two tendons, being naturally inserted, in such case, on 

 certain of the rays. The ventral fibers of the muscle are inserted 

 on a long, curved tendinous formation that forms part of the 

 muscle. This tendon, or aponeurosis, begins near the ventral end of 



