MR. J. W. DAYIS OX CnOXDROSTEUS ACIPEXSEROIDES. 



607 



suboperculum (32). The latter is 2-0 inches in breadth and 1*0 inch 

 in depth, ovoid in outline, with an acute angle behind and an obtuse 



Diagram of the Bones of the Head of Chondrosteus acipenseroides 



(One third natural size.) 



pf, postfrontal. 



fr, frontal. 



pa, parietal. 



nia, mastoid. 



so, supraoccipital. 



ex, exoccipital or petrosal. 



ss, suprascapular. 



km, hyomandibular. 



bs, basi sphenoid. 



sc, scapular. 



op, operculum. 



c, coracoid. 



sop, suboperculuni. 



r, radius. 



u, ulna. 



br, branchiostegal 



rays. 

 ch, ceratohyal. 



ht, hypotyinpamc. 

 mt, mesotympanic. 

 mx, maxilla. 

 md, mandible. 

 p, palatine. 

 as, alisphenoid. 

 ps, presphenoid. 

 to, infraorbital. 

 o, orbit. 



one in front. The external surfaces of the opercular bones are rudely 

 punctate, and exhibit a series of lines or striae radiating from the 

 upper anterior surface towards the margin. To the lower concave 



