32 OSTEOLOGY OF SCOMBROID FISHES 



Vertebrae in small numbers; the abdominal always 10; the caudal 

 from 14 to 16 (usually the former). 



Parapophyses not developed very far anteriorly; the last two or 

 three pairs with a bridge of bone connecting them; but they do not 

 (except in the Naucratinae) unite in pairs, each pair to form a single 

 haemal spine. 



Epipleurals anteriorly borne by ribs (only so in one genus of 

 Scombridoa). 



First interhaemal enlarged (except in the Naucratinae) and very 

 closely attached to the enlarged first hasmal process. 



Caudal rays rather deeply divided, usually not so much so as in 

 the Scombrida?, but more than in the Percoid fishes. 



Dorsal spines usually stiff and stout; dorsal and anal finlets some- 

 times present. 



Caudal peduncle slender and the caudal rays divergent. 



HYPEROSTOSIS. 



Many of the forms of this family have some thickened bones. These 

 are here described away from the main descriptions for better com- 

 parison. They are usually dense or ivory-like on the surface, but are 

 more or less cellular inside. Apparently they are a development of age 

 rather than of maturity. That entirely different bones may become 

 thickened in different species of the same genus, or between closely 

 related species, is shown in the two species of Caranx here decsribed. 

 It appears further from this material that where the bone thickening 

 occurs at all it occurs consistently in the same bones in individuals of 

 the same species. What individual variation may be expected, or what 

 taxonomic value the character may have, we have not enough material 

 at hand to say. As shown, however, by Selene and Citula, there may 

 be considerable variation in the size of the thickening, or it may not 

 develop at all in species that normally, or sometimes, have it at a cer- 

 tain age or size. There is no proof with this material that in the latter 

 case, where it has not occurred, it might not have developed with time. 

 The problem should be studied in some locality where a large number 

 of Carangoids of different ages may be examined. 



In Oligoplites niutidus, 18 inches in length, the frontals above the 

 orbital cavity are so thickened that the supraoccipital crest is nearly 

 obliterated. The frontals in this region are nearly y 2 i ncn i Q thick- 

 ness. On the lower end of the clavicle is a swollen area l 1 /^ inches 





