252 BR. W. G. RIDEWOOD ON THE 



On the Cranial Osteology of the Eishes o£ the families Osteo- 

 glossidw, Pantodontidce, and PhractolcBmidce. By W. G. 

 EiDEWooD, D.Sc, Lecturer on Biology at St. Mary's 

 Hospital Medical School, London. 



[Read 19tli January, 1905.] 

 (Plates 30-32.) 



An extensive investigation on the structure of the skull of the 

 lower Teleostean fishes which I began in the year 1896 has now 

 arrived at a stage of progress that warrants the publication of 

 certain of the results. Two papers have already appeared : one, 

 on the skull of the Elopidse and Albulidse, in the ' Proceedings 

 of the Zoological Society ' (1904, ii. pp. 35-81), and the other, on 

 the skull of the Mormyridse, Notopteridse, and Hyodontidse, 

 in the ' Journal of the Linnean Society ' (Zoology, xxix. 1904, 

 pp. 188-217). The present communication represents a third 

 instalment of the results ; a fourth, dealing with the skull of the 

 Clupeoid fishes, is rapidly approaching completion. 



Seven species of fishes are considered in this paper — three 

 species of Osteoglossum*, and one species of each of the genera 

 Ao^apaiina, Seterotis, Pantodon, and PliractolcBmus. These fishes 

 are all of freshwater habit, they are all tropical, and, with the 

 exception of Osteoglossum Leichardti of Queensland, all occur 

 within ten degrees of the Equator. Osteoglossum hicirrJiosum 

 and Arapaima gigas are found only in Brazil and Gruiana, Osteo- 

 glossum formosum in Borneo and Sumatra, and Seterotis nilo- 

 ticus, Pantodon Buchliolzi, and PhractolcBmus Ansorgii in Equa- 

 torial Africa. 



One of the most striking and characteristic features of the 

 skull of the Osteoglossid fishes is the occurrence of a paired 

 lateral peg of the parasphenoid bone for articulation with the 

 hyopalatine arch, described by Bridge in Osteoglossum formoswin 



* The Australian species of Osteoglossum was described by Giintber in 1864 

 under the name of Scleropages, but be afterwards withdrew the genus, con- 

 sidering his Scleropages Leicliardti to be a species of Osteoglossum. Boulenger, 

 however (Ann. Mag. Nat. Hist. (7) viii. 1901, pp. 514-515), has recently 

 found that Osteoglossuon bicirrhosum differs from 0. formosum and 0. Leichardti 

 in the number of vertebi-ffi, the position of the pelvic fins, and the number of 

 branchiostegal rays, and he proposes to re-establish the genus Scleropages for 

 the inclusion of the latter two species. 



