CARANGIDAE 37 



The crest carries a series of sensory tubes, which radiate outward from 

 its base to its edge. A sharp, high, superorbital rim is always distinct, 

 curving downward behind and below the pterotic crest. 



CRANIAL ELEMENTS. 



The exoccipitals are in contact with each other for their full length 

 along their upper edges, but as the supraoccipital overlies the suture 

 between them they appear on the surface of the cranium to be sep- 

 arated by the latter bone. They are also in contact along their lower 

 edges over the basioccipital, though in the small specimens of Trachin- 

 otus, and in Decapterus, they fail to meet at the mouth of the foramen 

 magnum. In the large specimen of Trachinotus, however, they meet 

 broadly in this region (the small and large specimens being of different 

 species, this may be either a variation of species or of age). The artic- 

 ular facets of the exoccipital condyles are not always contiguous above 

 the basioccipital, even when the exoccipitals are in contact just in front 

 of them. In Trachurus, Trachurops, Megalaspis, Naucrates, Oligoplites 

 and Decapterus they are separated. In the others they meet more or 

 less broadly. In the fusiform genera the exoccipital condyles slope 

 over the basioccipital condyle in a normal degree, but in the deep com- 

 pressed genera the former overhang the latter so much that their slope 

 towards each other forms a right angle. Decapterus is peculiar in hav- 

 ing the exoccipital condyles at the side and wholly below the level of 

 the upper edge of the basioccipital, while their posterior surface is a 

 little anterior to that of the basioccipital condyle. 



The supraoccipital is developed very far forward in the crest, ex- 

 tending in most cases to above the middle of the orbital cavity, but in 

 Trachinotus it extends to above the front of the orbital cavity, or 

 nearly the whole length of the frontals. In this genus the length of 

 the supraoccipital equals three-quarters of the length of the entire cra- 

 nium. Between these two conditions are all intermediate gradations. 



As viewed from the outside of the cranium the epiotics appear on 

 each side of the supraoccipital widely separated, but from the inside 

 their condition is various. In Oligoplites and Scomberoides the epiotics 

 meet for their full length at the median line, and the supraoccipital 

 can not be said to separate them in any degree. In Caranx they are 

 joined for about half of their length, while the supraoccipital separates 

 them above. In Megalaspis and Chloroscombrus they only narrowly 

 meet. In the others a wedge of the supraoccipital extends downward 

 between them, below which an area of cartilage separates them more 

 or less widely. 



