70 



PISCES 



CLASS I 



Read aiid branchial region covered with enamelled dermal hones. Teeth numerous, 

 acutehj conical, arranged on the horder of the jaws : enlarged laniary teeth in, a 

 second inner series on several separate splenial hones. The teeth distinguished hy a 

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



The only satisfactorily known genus referable to this family is Holoptychius, 

 Ag. {Ghjptolepis, Platygnathus, Ag.), (Figs. 124, 125), from the Old lied' 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 resemhling preceding family, hut hoth paired fins with a short, ohtuse lohe. 

 Teeth few and conical, with a loell-defined pulp cavity, the wall of which is radial ely 



Fio. 127. 



Rhizodm hihberti, Ag, 

 Tooth, I/o nat. size 

 Lower Carboniferous 

 Edüiburgh. 



folded in the lower part of the crown. 

 Usually several tooth -hearing splenial 

 hones on the inner side of the mandihle. 

 Devonian, Carboniferous, and Lower 

 Permian. 



lihizodus, Owen. (Megalichthys, Ag. 

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

 pletely known fishes with rough, 

 riigose cycloidal scales. Infraclavicle 

 with a long upwardly directed process. 

 Teeth smooth, compressed to a sharp 

 edge in front and behind. B. hihherti. 



Fig. 1-^b'. 



Rhizodopsis sauroides, Williamson sp. Outline re- 

 storatious of head and opercular apparatus from tlie 

 Upper (A), lower (B), and lateral (6) aspects, about 1/2 

 nat. size. Upper Carboniferous ; Staftbrdshire. ag, 

 Angular ; d, Dentary ; /, Frontal ; id, Infradeutary ; 

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

 mj, Median gular (jngular); mv, Mandible ; mx, 

 Maxiila ; ap, Operculuni ; or, Orbit ; pf, Postfrontal ; 

 priir, Premaxilla ; pop, Preopercnbun ; pa, Parietal ; 

 so, Suborbital ; sop, Suboperculum ; sq, Squaniosal ; 

 st, Supratemporal; r, ./;', Cheek-plates (after Tra- 

 quair). 



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

 umberland. Allied species in Coal Measures of North America. 



