70 



PISCES 



CLASS I 



Head and branchial region covered with enamelled dermal bones. Teeth numerous, 

 acutely conical, arranged on the border of the jaws : enlarged laniary teeth in a 

 second inner series on several separate splenial bones. The teeth distinguished by a 

 very complicated, meandering, folded structure (dendrodont). Devonian. 



The only satisfactorily known genus referable to this family is Hoi opt //chins, 

 Ag. (Glyptolepis, Platygnathus, Ag.), (Figs. 124, 125), from the Old Red Sand- 

 stone of Scotland, England, and Ireland, and from the Devonian of N.-W. 

 Russia, Bohemia, Belgium, the Eifel, the United States, Canada, and Green- 

 land. Several species attain a large size. Detached teeth have been 

 described as Dendrodus, Owen (Fig. 126); Lamnodus, Ag. ; and Apedodus, 



Leidy. 



Family 2. Rhizodontidae. Traquair. 



Closely resembling preceding family, but both paired fins with a short, obtuse lobe. 

 Teeth few and cortical, with a well-defined pulp carity, the wall of which is radio tely 





m 



T- 



FjG. 127. 



Rhizodus hihberti, Ag. 

 Tooth, !/o nat. size. 

 Lower Carboniferous ; 

 Edinburgh. 



folded in the lower part of the crown. 

 Usually several tooth -bearing splenial 

 bones on the inner side of the mandible. 

 Devonian, Carboniferous, and Lower 

 Permian. 



Rhizodus, Owen. (Megalichthys, Ag. 

 p.p.), (Fig. 127). Very large, incom- 

 pletely known fishes with rough, 

 rugose cycloidal scales. Infraclavicle 

 with a long upwardly directed process. 

 Teeth smooth, compressed to a sharp 

 edge in front and behind. R. hihberti, 

 Ag., and B. ornatus, Traq., from Lower Carboniferous, Scotland and North- 

 umberland. Allied species in Coal Measures of North America. 



Fig. 12S. 



Rhizodopsis sauroides, Williamson s]>. Outline re- 

 storations of head and opercular apparatus from the 

 upper (A), lower (B), and lateral (C) aspects, about 1/2 

 nat. size. Upper Carboniferous ; Staffordshire, ag, 

 Angular; d, Dentary;/, Frontal; id, Infradentary : 

 j, Principal gular (jugular) ; Ij, Lateral gular (jugular): 

 wj, Median gular (jugular); mm,, Mandible; nix, 

 Maxilla; op, Operculum; or, Orbit; pf, Postfrontal ; 

 pmx, Premaxilla ; pop, Preoperculum ; pa, Parietal; 

 so, Suborbital ; sop, Suboperculum : sq, Squamosal ; 

 st, Supratemporal ; x, <', Cheek-plates (after Tra- 

 quair). 



