398 
CR0SS0PTERYG1I. 
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 Coelacanthidae 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 (Lihys 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 . Coslacantkus (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) 
