CLASSIFICATION OF DEVONIAN FISHES. 



23 



the frontals, into a continuous shield, as seems to have been the 

 case in Dipterus. 



The upper part of the occipital region is covered by a number of 

 more or less irregular plates, which, however, may be readily shown 

 to correspond with dismemberments of the three plates found in the 

 Saurodipterini, &c. There are neither lateral, nor median, jugulars ; 

 the teeth have simple pulp cavities ; and what is most remarkable, 

 the dorsal fin, instead of being double, is incompletely broken up 

 into a number of pinnules, which extend for nearly the whole 

 length of the back. Furthermore, Polypterus has a spiracle, a 

 structure of which I find no trace in any of the fossil genera. 



It may conduce to clearness if, before proceeding farther, I now 

 endeavour to put the results of the preceding statements into a 

 readily comprehensible and definite form, and show their bearing 

 upon the classification of the Ganoids, and more particularly upon 

 that of the fossil Ganoidei. To this end I have prepared the follow- 

 ing synoptical table : — 



Ordo ganoidei. 



SuBORDO L — Amiad^. 



SUBORDO II. — LePIDOSTEII)^. 

 SuBORDO III. — CROSSOPTERYGlDiE. ° - 



Fam. 1 POLYPTERINI. 



Dorsal fin very long, multifid ; scales rhomboidal. 

 Polypterus, 



Fam. 2. — Saurodipterini. i 



Dorsal fins two; scales rhomboidal, smooth; fins subacutely lobatCo 

 Diplopterus^ Osteolepis, Megalichthys. 



Fam. 3.— Glyptodipterini. / 0 



Dorsal fins two; scales rhomboidal or cycloid al, sculptured; pec- 

 toral fins acutely lobate ; dentition dendrodont. 



Sub-fam. A. with rhomboidal scales. 



Glyptol(BmuSy Glyptopomus] Gyroptychius. 



Sub-fam. B. with cycloidal scales. 



Holoptychius, Glyptolepis, Plafygnathiis \_Rhizodus, Den- 

 drodus, Cricodus, Lamnodus']. 



