No. 2.] AM/A AND TELEOSTS. 95 



and the other the homologue of the post-occipital or first free 

 spinal nerve. The latter nerve, although wanting in the Chara- 

 cinidae, is said to be found in Silurus glanis, and to lie in that 

 fish between the claustrum and stapes. 



There are thus, according to Sagemehl's descriptions, ex- 

 actly the same number of spinal, or spinal-like, nerves indi- 

 cated in the occipital part of the skull of the Characinidae as 

 are found in Scomber, and they have exactly the same relations 

 to the vertebral components of the skull. The same is true, 

 according to his descriptions (No. 5, pp. 527, 543), of many 

 other teleosts, among which may be mentioned Esox, Umbra, 

 Perca, the Gadidae, Cyprinodontidae, and Cyprinidae. In the 

 Cyprinidae the nerve c is said to be wanting, as it is in the 

 Characinidae. In the other fishes named, excepting Esox, it 

 is said to be found. Whether it is or is not found in Esox is not 

 stated. Fiirbringer, however, gives it in this fish (No. 2, p. 

 466). In the Characinidae, Fiirbringer gives nerve 4, differing 

 in this from Sagemehl. He agrees with the latter author as to 

 the absence in these fishes of nerve c. My work would incline 

 me to think that the nerve considered by both these authors as 

 nerve b was in reality nerve c, and that nerve b had been missed 

 by both of them in dissection. 



In Carassius, Sewertzoff says (No. 8, p. 423) there are three 

 dorsal vertebral arches in the occipital part of the skull. In 

 Amia I found (No. i, p. 727) that the same number of arches 

 were indicated in the region occupied by the cartilaginous 

 occipitale laterale, and that this number of vertebral arches 

 corresponded to the number of muscle-segments. The muscle- 

 segments in Scomber indicate a similar number of vertebral 

 arches in the occipital part of the skull of that fish. Scomber 

 thus agreeing in this with Carassius. 



In Salmo salar, Harrison (No. 3) gives two persistent occipi- 

 tal muscle-segments, and says that a third and more anterior 

 segment, found in embryos twenty-four days old, disappears 

 entirely after that age. The first persistent segment is said to 

 have no spino-occipital nerve related to it. The second segment 

 is said to be related to the hypoglossus, which nerve in young 

 stages is found "von demselben Bau als die ubrigen " spinal 



