﻿RHIPIDISTIA. 



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extending its whole length, flanked by a pair of squamosal elements 

 in the hinder half, and usually also by a pair of postfeontal plates 

 in front of these. The posterior half of the frontal shield is formed 

 by the frontal bones, which extend from side to side, and are some- 

 times fused together in the middle line, with or without a median 

 (pineal) foramen ; the anterior extremity of the shield consists of 



Fig. 47. 



Ehizodopsis sauroides (Williamson). — Outlines of head and opercular appa- 

 ratus, after Traquair. A. Side view. B. Upper aspect. C. Inferior aspect. 

 ag, angular ; d, dentary ; /,frontal ; i.d, infradentary ;j, principal jugular ; 

 l.j, lateral jugular ; m.j, median jugular ; mx, maxilla ; mn, mandible ; 

 op, operculum; or, orbit; p.f, postf'rontal ; p.mx, premaxilla ; p.op, 

 preoperculum ; pa, parietal; s.o, suborbital: s.op, suboperculum ; s.t, 

 supratemporal ; sg, squamosal; a-, cheek-plate ; x', (?)jugal. 



the dentigerous prem axillae, usually fused together, and also more 

 or less in connection with the irregular small dermal plates which 

 intervene between them and the frontals. The cheek is entirely 

 covered with loose plates, of which the suborbitals behind and 



