8 ELOPIFORM FISHES 



branches. Union of infraorbital, antorbital and ethmoid commissure sensory canals 

 lying within skin. Supramaxillae narrow, posterior member without strengthening 

 ridge. Quadrate with anterior and posterior margins of equal length. Ceratohyal 

 imperforate. Preoperculum with a slight posterior expansion, the contained sensory 

 canal running at the anterior margin of the bone and opening to the surface by 

 numerous pores. Vertebral count high, averaging 75. Caudal fin without fringing 

 fulcra. 



Type-species. Elops saurus Linnaeus, 1766. 



Remarks. Although many references have been made to Elops in discussions 

 of teleostean phylogeny, no complete osteological description exists. The direct 

 relevance of such a study to a work of this nature justifies the inclusion of a descrip- 

 tion here. Elops hawaiensis Regan has been chosen as the species to be described 

 since the size range of available individuals allows an evaluation of ontogenetic 

 changes. 



Regan (1909) recognized seven species of Elops ; E. saurus Linnaeus from the 

 east coast of Middle America and E. affinis Regan from the west coast, E. sene- 

 galensis Regan and E. lacerta Cuvier & Valenciennes from the west coast of Africa, 

 E. machnata Forskal, E. hawaiensis Regan and E. australis Regan from the Indo- 

 Pacific. The differences between these species are primarily differences in gill-raker, 

 vertebral and scale counts. Whitehead (1962) did not consider E. australis a valid 

 species and placed it in synonymy with E. hawaiensis. E. machnata is also very 

 much like E. hawaiensis, differing only in vertebral counts (63-64 in the former 

 against 66-69 in the latter) and by the fact that when the mouth is closed the pre- 

 maxillary tooth band is exposed in E. hawaiensis but is covered by the lower jaw 

 in E. machnata (Regan 1909 ; Whitehead 1962). Both of these differences appear 

 to be trivial. The former is particularly unsatisfactory while specimens of both Indo- 

 Pacific species show variable conditions of the ' exposed ' or ' covered ' state. It is 

 likely that only one Indo-Pacific morphospecies exists. 



The differences between E. hawaiensis and the type-species are slight and have 

 been illustrated by Whitehead (1962). Certain portions of the osteology of Elops 

 have been satisfactorily described in recent literature and where this has been done 

 the relevant references are cited without further comment. 



Elops hawaiensis Regan, 1909 

 (Text-figs. 1-11) 

 1909 Elops hawaiensis Regan : 37. 



Diagnosis. See Regan [op. cit.). 



Habitat. Coastal waters of the Indo-Pacific. 



Description. Neurocranium. The neurocranium is three times as long as 

 deep. The maximum width of the cranium occurs at the occiput and is equal to 

 one and a half times the depth of the neurocranium. The cranial cavity occupies 

 about one-third of the total neurocranial length. 



