COMPARATIVE STUDY OP SCOMBROID PKHES. 345 



ftnd is insei-ted between the two moieties of the fin-ray. 



The lattn'a.1 nmrgin of the distrtl stigmcnts and that of the dorsal posterior 

 end of the proxiuud segment are mostly serrated in the ThumiidiW!, Lut is 

 strjugbt and entire in the Katsuwouidae. 



MUSCULAR SYSTEM. 



I have chie£y examined the kt^'.ral mnsclt!, the other muscles were scarcely 

 touchwl. Tlie gi'eat Literal muscle is originally composed of as many transverse 

 segments as there are vertebrae, and each segment is attached internally to 

 the respective veiiebra and its processes and ap^xaidages, — neural and 

 haemal processes, ribs, and intermuscular bones. The first thi-oe muscle- 

 segments, however, do not correspond to the first three vertebrae, as these 

 three segments belong to the cephalic, or rather occipital region, where wo 

 find one or two ansihixry intermuscular banes between them, in the CybiicLie 

 and Plecostei. These cephalic myotomes are inserted between the foramen 

 magnum and the pterotic processes of the cranium, and connects the skull with 

 the pectoral girdle. Hence the fourth muscle-segment or myotome corresponds 

 to the body-segment of the first vei-tebra. Moreover, some myotomes seem 

 sometimes to augment by subdivision, in fishes of the Katsuwouidae. In Auxis 

 one or two auxiliary myotomes are added iu the hypaxiai half. Generally one 

 anxiliaiy myotome is added near the boundary between the precaudal and 

 caudal portions. When there is another pusiliary myotome, it is fomid in the 

 anterior paii of the precaudal r^on, where the cutaneous artery appears to 

 the sm'fixce of the body. These auxiliary myotomes are Jiot always bilatei'ally 

 symmetiücal. Moreover two auxiliary myotomes ai'e sometimes found in one 

 side, and only one in the other. At the caudal region some myotomes arti 

 coalesced and they are much elongated anteriorly. The myotomes in the caudal 

 peduncle ai'e united into one in the Plecostei, in the region where the Literal 

 keel makes its appearance in the vertebrae, and where the neural and haemiil 

 processes are broad and horizontal. Thus in the anterior part of the adult 

 fish, the number of myotomes is greater thfin that of the vertebrae, and in 

 the caudal region the number is reduced from the confluence. The cephalic 

 myotomes as well as some following myotomes project anteriorly as a triangula^ 

 mass, and their thin, dorsal Umb is bent foi'wards along the dorsal median 



