46 OSTEOLOGY OP SCOMBROID FISHES 



extends to, or very slightly encroaches upon, the supraoccipital or the 

 parietal. The lower limb of the posttemporal is attached directly to the 

 opisthotic without the intervention of a ligament. In Trachinotus the 

 posttemporal is scarcely forked at all. Its lower end is very wide and 

 its lower fork is exceedingly thick and heavy, being but little produced 

 beyond the general outline of the bone. It forms an unusually broad 

 union with the opisthotic. 



The pelvic gridle is in no way notable. Each side rises along its 

 inner edge at the median line to form a low ridge, while at the outer 

 edge each side turns downward and is divided into two longitudinal 

 wings, with often a more or less evident third wing between. At the 

 posterior union of the sides a spine-like process is sent forward below 

 from the base of the ventrals, and above a forked process is sent back- 

 ward over the base of the ventrals. 



The Vertebral Column, Ribs, and Fin Elements. 



The number of the abdominal vertebrae in all of the forms here 

 considered is 10. The number of the caudal vertebrae is 14 in all but 

 Naucrates and Caranx chrysos, which have 15 (though Caranx hippos 

 has 14), and in Oligoplitcs and Scomberoides, which have 16. 



The parapophyses are not developed very far forward. From three 

 to five are usually present, though one or two undeveloped ones may 

 be present in front of these in some forms (they appear so gradually 

 it is difficult to be exact as to the number of developed ones). The 

 last two or three (in Alectis one) of them are connected with their 

 opposite fellows by a bridge of bone, leaving a hasmal canal above, and 

 their points projecting separately below. The first hsemal process is 

 differentiated from the last connected parapophyses by being single 

 pointed and much longer and stronger, so that the vertebral column is 

 sharply divided into an abdominal and caudal portion, aside from the 

 indication of this division by the attachment of ribs and anal fin. 



Seriola and Naucrates are exceptions to these rules. These forms 

 approach the Scombridae in having the posterior pair of parapophyses 

 united into a single spine, with the ribs at its tip, and the first haemal 

 process not abruptly enlarged or otherwise differentiated from it. 

 Decapterus approaches this condition in having the last pair of para- 

 pophyses united into a rounded arch, but with scarcely a spine devel- 

 oped, the ribs not in contact, and the first haemal process considerably 

 enlarged. 



The zygopophyses are usually very large and resemble those of the 

 Scombridae. On the upper surface of the front of each vertebra a flat 



