RHIPIDISTIA. 
319 
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 
Tig. 47. 
Bhizodopsis sauroides (Williamson).—Outlines of head and opercular appa¬ 
ratus, after Traquair. A. Side view. 33. Upper aspect. C. Inferior aspect. 
ag, angular ; d, dentary;/frontal; i.d, infradentary;/principaljugular; 
l.j, lateral jugular ; m.j, median jugular ; mx, maxilla ; ran, mandible ; 
°P> operculum; or, orbit; p.f , postfrontal; p.mx, premaxilla; p.op, 
preoperculum; pa, parietal; s.o, suborbital; s.op, suboperculum; s.t, 
supratemporal; sg, squamosal; x, 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 
