74 
ACTINOPTERYGII. 
single series ; minute styliforni or conical teeth on some of the 
inner bones and tongue. Suboperculum and interoperculum rudi¬ 
mentary or absent; branchiostegal rays slender, about 10 to 20 in 
number, and no gular plate. Vertebral centra well ossified, and 
those of the abdominal region with robust transverse processes for 
the support of the well-developed ribs ; a compound hypural bone 
at the base of the tail. Intermuscular bones present. Ein-fulcra 
absent ; fin-rays more or less divided and articulated distally; 
dorsal and anal fins remote and more or less extended. Scales 
thick and cycloidal, mosaic-like in structure, deeply imbricating. 
The surviving members of this family are confined to the fresh- 
waters of the tropics. Osteoglossum occurs in Tropical America, 
Australia, and the East Indies Arapaima is eharacteristic of 
Erazil and the Guyanas; while Beterotis is a Tropical African 
genus. 
The only extinct genus referable with certainty to the Osteo- 
glossidae is Dapedoglossus, from the freshwater Eocene of North 
America. Bryclicetus^ from the marine London Clay of Sheppey, is 
also probably a member of the same family; but its scales, so far 
as known, do not exhibit the characteristic mosaic-like structure. 
Genus DAPEDOGLiOSSUS, Cope. 
[Bull. U.S. Geol. Surv. Territ. vol. iii. 1877, p. 807.] 
Syn. Phareodus, J. Leidy, Proc. Acad. Nat. Sci. Philad. 1873, p. 99 
(undefined). 
Trunk much laterally compressed, comparatively short and deep, 
and abdomen trenchant. Cleft of mouth extending to a point 
below the middle of the orbit, the mandible not prominent, the 
marginal teeth long and slender, the inner teeth smaller, stout, 
short and conical, apparently borne by the vomer, palatines, 
tongue, and basihyals. Branchiostegal rays in uncertain number, 
but more than 10. Vertebrae about 45 in number, more caudal 
than abdominal. Pectoral fins with thickened and excessively 
elongated anterior ray; pelvic fins small; dorsal and anal fins 
directly opposed, the latter at least as much extended as the 
former, and well-separated from the caudal fin, which is very 
slightly excavated at its hinder margin. Scales large, displaying 
characteristic reticulate structure. 
^ Some points in the cranial osteology of Osteoglossum are described by 
T. W. Bridge, Proc. Zool. Soc. 1895, p. 302, pi. xxii. 
