22 ELOPIFORM FISHES 



Cephalic sensory canal system. The main canals run within bony tubes which are 

 perforated by pores. ' The sensory canals produce ridges upon the bones through 

 which they run. The junctions between the major canals lie in the skin. 



The lateral line passes on to the cranial roof by a pore at the postero-lateral 

 corner of the pterotic. The otic canal runs through the extreme lateral edge of the 

 roofing portion of the pterotic and opens anteriorly above the autosphenotic spine. 

 The dorsal surface of the otic canal is perforated by three or four pores. The pos- 

 terior opening of the otic canal lies adjacent to a pore in the supratemporal and also 

 adjacent to but at a distance from the top of the preopercular canal. The triradiate 

 union between the supratemporal commissure, otic and preopercular canals occurs 

 within the skin. 



The anterior opening of the otic canal lies adjacent to two pores ; one within the 

 frontal which is the lateral opening of the supraorbital canal and one from the dorsal 

 surface of the dermosphenotic which represents the dorsal limit of the infraorbital 

 canal. Again, the union of these canals lies in the skin. 



From its union with the otic and infraorbital canals, the supraorbital canal curves 

 medially and then anteriorly to run the length of the frontal. A large branch of 

 the supraorbital canal is given off posteriorly and this runs back on to the parietal 

 where it opens to the surface by a single terminal pore, behind which there is in some 

 specimens a continuing shallow groove. The groove is interpreted as representing 

 the anterior pit-line. The parietal is also marked by three small pores arranged in a 

 transverse row. Such a pore arrangement is similar to the middle pit-line of hale- 

 costomes and leptolepids. In these latter fishes the pores are set in a shallow groove 

 but no such connecting groove exists in Elops. The main supraorbital sensory canal 

 opens to the surface by several pores on both the lateral and medial aspects of the 

 canal. Above the epiphyseal region there is a predominance of medial pores, while 

 above the orbit and otic regions lateral pores are more common. 



The infraorbital canal runs very close to the orbital margin of the infraorbitals, 

 opening to the surface by a series of posterior and inferior pores. The neuromast 

 distribution has been noted by Nelson (1969b). Anteriorly the infraorbital canal 

 joins with the antorbital branch and the ethmoid commissure. The distribution 

 of the sensory canals in this region has been described by Nybelin for Elops lacerta 

 (1956, 1967a) which in all respects is similar to E. hawaiensis. 



The preopercular canal runs at the anterior margin of that bone and in its ventral 

 half opens to the surface by ten to fifteen pores. Ventrally the preopercular canal 

 is continuous with the mandibular canal which is contained within the articular and 

 dentary. The mandibular canal opens to the surface by a series of large pores. 



Opercular series. The opercular bones of Elops saurus have been described by 

 Ridewood (1904). In most respects they are similar to those of E. hawaiensis, 

 differing only in proportions. Further description is unnecessary. 



Pectoral girdle and fin. The supratemporal, although not strictly part of the 

 shoulder girdle, may be considered here. As in all elopoids the supratemporal is 

 very large and thin, fully justifying its alternative name of the ' scale bone '. The 

 supratemporal has a straight anterior margin which extends from the postero-lateral 

 corner of the pterotic to the mid-line. The posterior margin is broadly curved, 



