﻿398 CR0SS0PTEKTG1I. 



composed of a number of superposed lamellae ; and the inner face is 

 described by von Zittel as exhibiting large reticulating rugae, 

 suggestive of the network made known by Owen in the lung-like 

 air-bladder of the recent Protopterus. 



In all known genera, imbricating scales are present over the 

 whole of the trunk, and the superficial layer of ganoine is not con- 

 tinuous, but arranged in tubercles and striae. The lateral line is 

 either inconspicuous or leaves no impression upon the scales. 



Though ranging from the Lower Carboniferous to the Upper 

 Chalk, the skeletal characters of the Ccelacanthidae exhibit little 

 variation ; and it is difficult to recognize differences sufficiently 

 marked to be regarded as justifying the subdivision of the family 

 into a series of genera. The arrangement and proportions of the 

 fins are almost constant, the supplementary caudal being apparently 

 the only variable element. The other more important features 

 available for generic diagnoses are (i) the ornamentation or other- 

 wise of the head, opercular apparatus, and scales ; (ii) the presence 

 or absence of denticles upon the fin-rays ; and (iii) the more or less 

 jointed or non-jointed character of the rays themselves. One or two 

 genera (Libys and Heptanema) are also apparently characterized by 

 the relatively great development of the mucus-canals upon the head. 



With regard to specific characters, imperfections in the pre- 

 servation of the specimens render their precise determination often 

 impossible. The number of rays in the median fins, especially the 

 principal caudal, seems to vary in different species of the same 

 genus ; though this character can only be noted when there appears 

 to have been no displacement of parts in the fossil. Minor vari- 

 ations in scale-ornament, and the ornamentation and proportions 

 of the head and opercular bones, may also be cited as specific 

 differences. 



Synopsis of Genera. 



I. No denticles or tuberculations on fin-rays. 

 Superficial ornament of more or less discon- 

 tinuous ridges ; supplementary caudal fin 



prominent Ccdacanthv.s (p. 399). 



II. Denticles or tuberculations on preaxial rays of 



anterior dorsal and caudal fins. 

 A. Fin-rays with numerous close articulations ; 

 supplementary caudal fin prominent. 

 No parafrontal pits; superficial ornament 

 mostly tubercular ; fin-rays very robust, 

 articulated nearly to the base ; supple- 

 mentary caudal stout Graphiurus (p. 409) 



