154 ELOPIFORM FISHES 



and disposed vertically. Vertebral column of 72-76 vertebrae. Caudal centra as 

 long as deep and marked laterally by two grooves. Dorsal and anal fins without 

 elongated terminal fin-ray. Caudal fin without fringing fulcra, preural neural 

 spines expanded antero-posteriorly. Dorsal fin situated in the centre of the back. 

 Anal fin nearer to the caudal peduncle than to the pelvic fin. 



Type-species. Esox vulpes Linnaeus. 



Albula vulpes (Linnaeus), 1758 

 (Text-figs. 75-84) 



For synonymy see Hildebrand (1963). 



Diagnosis (emended). Albula in which the preorbital distance is considerably 

 less than half the total neurocranial length. Quadrate/mandibular articulation 

 beneath the lateral ethmoid. Parasphenoid, endopterygoid and basibranchial 

 teeth of variable size, there being a decrease in average tooth size towards the edges 

 of all tooth plates. Depth of neurocranium at the autosphenotic level equalling 

 26-28 per cent of the neurocranial length. Sub-epiotic fossae without ridges along 

 the medial borders. Operculum slightly deeper than wide. Cranial roofing bones 

 smooth. Dorsal fin with 17-19 rays, anal with 8-9. 



Habitat. All tropical and subtropical seas ; in shallow water. Hildebrand 

 (1963) gives a general account of Albula vulpes and refers to literature on the biology 

 and ecology of the species. 



Remarks. Albula vulpes is often cited in literature. The descriptions of the 

 cranium given by Ride wood (1904) and of the tail given by Hollister (1936) are 

 particularly good. The comparative description given below is intended to supple- 

 ment those works. 



Description. Neurocranium. The relative dimensions of the neurocranium 

 are similar to those of Pterothrissus . Thus it is long and shallow, the snout is narrow, 

 the otic bullae are large, the subtemporal and sub-epiotic fossae are deep and the 

 small post-temporal fossae are inclined antero-medially. As in all albulids the 

 neurocranium is more heavily ossified than in Pterothrissus. 



The skull roof (Text-fig. 75) shows several features commonly met with among 

 albulids. The frontal is large with a deep trough anteriorly. Posteriorly the frontal 

 reaches well back resulting in a small pterotic and parietal. The parietal is broader 

 than long and of irregular shape. The nasal is large and in some specimens is 

 ossified in two units, an anterior and posterior nasal ossicle. 



The dermethmoid is of a more complicated shape than it is in pterothrissids. 

 The dermethmoid of A. vulpes is raised to form a median ridge which, as in ptero- 

 thrissids, is braced anteriorly by inclined struts. Anteriorly the dermethmoid 

 ridge is widest dorsally where it shows a well-marked central groove that is covered 

 in life by taut skin. Posteriorly the walls of this groove form ridges which pass 

 postero-laterally and ' fade out ' on the frontals. At the point where the ridges 



