﻿osteolepid^;. 367 



Family OSTEOLEPID^E. 



Body fusiform, robust, elongated, and somewhat depressed, with 

 rhomboidal scales, slightly overlapping, and covered externally with 

 a more or less continuous layer of ganoine. Head and opercular 

 apparatus with well-developed membrane- bones ; parietals large 

 and separate ; frontals separate, or fused together and with the 

 adjoining elements, in which case a median frontal foramen is 

 conspicuous ; orbits far forwards ; interoperculum absent ; jugular 

 plates comprising one large pair, flanked on either side by a lateral 

 series, and with or without a small azygous element in front. 

 Dentary bone of mandible fused with well-developed infradentaries in 

 the same plane, and forming a thin vertical lamina ; an inner series of 

 few large, narrow, shuttle-shaped bones, also fused with the dentary, 

 and each supporting a " laniary " tooth ; a pair of similar teeth on 

 the roof of the mouth, but the marginal upper dentition feeble. 

 Teeth conical, with a pulp-cavity, of which the walls are not 

 folded, except quite at the base. Pectoral and pelvic fins obtusely 

 lobate ; two remote dorsal fins, the first nearly opposite or directly 

 opposite to the pelvic pair ; anal fin single ; caudal fin diphycercal 

 or heterocercal. 



In the four typical genera of this family some of the anterior 

 rays of each of the fins are relatively robust and covered with 

 ganoine. This appearance is due, according to Pander, to the in- 

 vestment of the rays with true scales. 



/Synopsis of Genera. 



I. Scales smooth and punctate. 



A pineal foramen ; dorsal fins alternating 



with pelvic and anal ; tail heterocercal . . Osteolepis (p. 368). 

 A pineal foramen ; dorsal fins opposed to 



pelvic and anal; tail heterocercal Thursius (p. 373). 



A pineal foramen ; dorsal fins opposed to 



pelvic and anal; tail almost diphycercal 



' and caudal fin rhomboidal Diplopterus (p. 375). 



No pineal foramen ; dorsal fins opposed to 



pelvic and anal ; tail almost heterocercal . . Megalichthys (p. 378). 



II. Scales sculptured. 



Anterior dorsal fin opposed to pelvic pair: 

 tail diphycercal , Glypiopomus (p. 



