70 



PISCES 



CLASS I 



Head and branchial region covered with enamelled dermal hones. 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 Holoptyrhius, 

 Ag. {Glyptolepis, Platygnathus, Ag.), (Figs. 124, 125), from the Old Eed 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 Denxlrodus, 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 conical, tvith a tvell-defined pidp cavity, the tvall of which is radiately 



Rhizotlus hihberti, Ag. 

 Tooth, 1/2 uat. size. 

 Lower Carboniferous;; 

 Edinburgh. 



folded in the lower part of the croicn. 

 Usually several tooth-hearing splenial 

 bones on the inner side of the viandible. 

 Devonian, Cai'boniferous, and Lower 

 Permian. 



Bhkodus, Owen. {Jlegalichthys, 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. B. hihberti, 



Fig. iL't--. 



Ehizodopsis savroiiles, William.son sp. Outline re- 

 storations of head and opercular apparatus from the 

 upper (A), lower (B), and lateral (C) aspects, about i/.i 

 nat. size. Upper Carboniferous ; Statlbrdsliire. ag, 

 Angular; il, Dentary ; /, Frontal; id, Infradentarj' ; 

 j. Principal gular (.jugular); //, Lateral gular (jugular); 

 mj. Median gular (jugular); mit. Mandible; m.r. 

 Maxilla ; op, ()perculum ; or, Orbit ; itf, Postfrontal ; 

 piiu; Premaxilla ; jwp, Preoperculum ; p«. Parietal : 

 so. Suborbital ; sop, Suboperculuin ; sij, Squamosal ; 

 st, Suprateuiporal ; x, x'. Cheek -plates (after Tra- 

 quair). 



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

 umberland. Allied species in Coal Measures of Xorth America. 



