990 mr. h. m. kylb oy St [Dec. 18, 



made out, aud so can those of the subopercular. interopercular, and 

 opercular boues, but not so readily. 



The bones forming the mouth are much more developed on the 

 blind than on the eyed side — the distances of the tip of the snout 

 from the lower extremities of the premaxillary boues being in 

 the proportion of 4 to 3, the greater being that of the blind side. 

 Similarly, the proportion between the under and upper rami of 

 the lower jaw is as 6 to 5. The under ramus (that of the blind 

 side) is inclined backward from the mouth at a greater acute augle 

 than the upper ramus, so that the latter overlaps the former. 

 This can readily be seen from the under aspect (fig. 2, p. 987). 

 The mouth thus asymmetrical like that of the Plaice group, is also 

 small, the length of the premaxilla of the blind side being 24 per 

 cent, of the length of the head measured from the snout to the 

 posterior margin of the opercular bone. The posterior extremity 

 of the mandible on the upperside is in a vertical line with the 

 anterior extremity of the lower eye. There are no teeth on the 

 upper or eyed aspect of the mouth, but on the lower aspect there 

 are two rows of small sharply-pointed teeth on the mandible aud 

 premaxilla. These teeth are closely set and seem movable out and 

 in, those of the premaxilla beiug more extended than those of the 

 mandible. On the latter, the inner row stops about halfway, and 

 a few teeth placed externally to the outer row continue the double 

 series. There are uo teeth on the maxilla; or vomer. 



When the maxilla? and interrnaxilla? are pulled outward, it is seen 

 that they are overhung by a definite snout (fig. 3, p. 987) formed 

 by the first interspinous ray, which is inclined forward from the 

 anterior margin of the upper eye along the ridge of the head. 

 The nasal organs lie one on each side of the dorsal fin as in the 

 Turbot group : that of the eyed side lies between the iuterorbital 

 ridge and the maxillary bones in the space between the latter 

 bones and the ethmoid ; that of the blind side lies immediately 

 under the second and third rays of the dorsal fin (fig. 2). The 

 posterior nostrils are simple, oval in outline, whilst the anterior 

 are overhung by a triangular flap. The internal structure of the 

 olfactory orgau is similar to that of the Plaice group, t. e. the 

 epithelial lamina?, which are well-developed, are disposed longi- 

 tudinally to the main axis of the body. There are no secretory 

 sacs. The gill-opening is large and open. The gill-covers, though 

 overlapping the margins of the pectoral arch and ventral fins, are 

 free therefrom. The septum between the branchial cavities is 

 unbroken. The gill-rakers are short, soft, denticulated, and very 

 numerous, set in two rows on each arch, the outer row of the first 

 arch on the eyed side having 29 rakers, the inner row of the same 

 arch about 12. The pharyngeal teeth are small and pointed. The 

 branchiostegal membranes meet but do not cross in the median 

 line. The first three rays on the ceratohyal are slender, whilst the 

 remaining four on the epihyal are long and well -developed. 



The internal organs are similar in some respects to those of the 

 Sole group. There are no pyloric ca?ca. Along the dorsal wall 



