172 ELOPIFORM FISHES 



supramaxilla. Quadrate/mandibular articulation beneath posterior half of the orbit. 

 Suboperculum large, equal in area to half that of the operculum. Gular plate large. 

 Vertebral column with 64-66 vertebrae of which 23-24 are caudal. Centra deeper 

 than long, marked laterally by 5-6 grooves. Anal fin situated nearer to caudal 

 peduncle than to the pelvic fin. 



Type species. Osmeroides gracilis Davis. 



Lebonichthys gracilis (Davis) 



(Text-figs. 88-91) 



1887 Osmeroides gracilis Davis : 559, pi. 31, figs. 2, 3. 

 1887 Osmeroides latus Davis : 561, pi. 31, fig. 1. 

 ? 1887 Osmeroides brevis Davis : 560, pi. 32, fig. 1. 

 1901 Osmeroides gracilis Davis ; Woodward : 16, pi. 2, figs. 1, 2. 



Diagnosis. Lebonichthys reaching 170 mm S.L. Head and opercular apparatus 

 equal in length to 30 per cent of standard length. Parasphenoid with hemispherical 

 teeth of irregular size. Ectopterygoid edentulous. Maxilla edentulous. Dorsal 

 fin situated nearer to the occiput than to the caudal peduncle, with 24-25 rays. 

 Caudal skeleton with three epurals, supporting neural spines unexpanded, fringing 

 fulcra and caudal scutes present. Scales with anterior margin scalloped. 



Holotype. Incomplete fish, R.S.M. 1891.59.86, from the Upper Santonian of 

 Sahel Alma, Lebanon. 



Material. The holotype and 16 specimens in B.M.N.H. All specimens are 

 from the Upper Santonian of Sahel Alma, Lebanon. 



Description. The head occupies 30 per cent of the standard length and is twice 

 as long as it is deep. The anterior end of the snout is slightly truncated. The 

 quadrate/mandibular articulation lies beneath the centre of the orbit. With the 

 exception of the frontals and pterotics, the cranial bones are smooth. 



Neurocranium. The neurocranium is shallow throughout. The roof is flat with 

 the frontals forming the majority of its area. Each frontal meets its partner in a 

 slightly wavy suture. Anteriorly the dermethmoid, which is smaller and simpler 

 in shape than that of Albula, separates the frontals. The frontal tapers gradually 

 toward the snout but there are two places where the frontal narrows sharply, at the 

 level of the autosphenotic spine and again at the level of the lateral ethmoid. Pos- 

 teriorly the frontal is indented where it meets the pterotic. The surface of the frontal 

 is slightly raised at the centre of ossification. From this centre several ridges, 

 with intervening grooves, curve anteriorly and laterally. The most medial of these 

 ridges ends anteriorly in a foramen which marks the point of exit from the bone of 

 the supraorbital sensory canal. Anterior to this level the canal continued in a 

 shallow groove. The central portion of the skull roof exhibits a slightly depressed 

 area. Faint ridges may also be seen passing posteriorly from the ossification centre 

 of the frontal but these are weak compared to the anterior ridges. 



