GLYPTOLiEMUS KINNAIRDI. 43 



The post-frontals, better defined posteriorly than anteriorly, 

 appear to join the prefrontals, and then, extending backwards beyond 

 the posterior margins of the frontals, they unite with the anterior 

 moiety of the parietals, filling up all that notch in the outer border 

 of these bones, which has been described. Their posterior edges are 

 connected, internally, with the anterior margins of the projecting 

 part of the parietal, externally with the same margins of the small 

 quadrilateral squamosal bones. 



The posterior part of the supero -lateral region is completed by 

 two squamiform bones, which take the place of the external occi- 

 pital, or epiotic, bones of other fishes, filling the interspaces left 

 between the supraoccipital and the opercular apparatus. The inner 

 surface of this bone, on the left side, presents a very well marked 

 triradiate impression, one crus of which is directed transversely 

 inwards, while the others are respectively directed forwards and 

 backwards. A shallow groove upon the surface of the supraocci- 

 pital, which has a slight concavity forwards, connects the trans- 

 verse crus of the impression on one of these bones with that on the 

 other. 



The triradiate marks are much more distinct upon the inner 

 surface of these bones, where they form distinct ridges, than upon 

 the outer surfaces, where they appear only as very shallow and in- 

 distinct grooves ; and, except for the continuation of each transverse 

 crus into its fellow across the supraoccipital, I should have been 

 disposed to connect them rather with the semicircular canals of the 

 auditory organ than with the so-called mucous grooves. 



The lateral regions of the skull behind the premaxillaries are 

 formed, in front of the orbit, by the prefrontal and maxillary, and 

 behind the orbit, first, by the maxilla and a large post orbital bone, 

 then by the maxilla, by the bone marked P.O., which may very likely 

 not be a true preoperculum, and a large supratemporal bone. The 

 latter articulates above with the postfrontal and squamosal, and 

 fits posteriorly into the notch formed by the vertical and horizontal 

 portions of the bone P.O. 



The operculum, a large four-sided bony plate, is connected with 

 the outer edge of the epiotic above and with the posterior edge of 

 the ascending ramus of the bone P.O. in front. Its lower edge 

 articulates with the upper margin of the suboperculum, which is 

 about half as large as the operculum, and has a much more rounded 

 posterior edge. 



The palato-quadrate arcade is best exhibited in fig. la, Plate I., 

 though the lines of demarcation between its constituents are not 



