Sir J. Richardson un Australian Fish. 291 



densely crowded as to form nearly the whole of their smooth exterior 

 surfaces. 



Olisthops cyanomelas, Richardson. 



Radii.— Br. A; D. 18|10; A. 3|10; C. 12|; V. \\5 ; P. 12. 

 .' Form elongated, the greatest height of the body, which occurs just 

 behind the ventrals, being contained iiA^e times and a half in the total 

 length of the fish, caudal included. The bluffness of the head, pro- 

 duced by the form of the jaws, is intermediate between that of Scarus 

 and Odax, and the profile, from the nostrils to the dorsal, is mode- 

 rately ascending and but slightly convex. The jaws have the usual 

 structure of those of Scarus, being composed of a multitude of mi- 

 nute teeth, arranged in a quincuncial order in many rows, and so in- 

 corporated with the bone that they produce no inequality of surface, 

 but reflect the light in certain positions so as to reveal their struc- 

 ture. The two premaxillaries conjointly, and the two halves of the 

 mandible, resemble half the bowl of a spoon with straight cutting edges, 

 which under a lens appear to be striated and minutely crenulated. 

 At the symphysis of the mandible, the cutting edge rises slightly, so 

 as to seem very slightly peaked. The orifice of the mouth is com- 

 paratively small, and the small maxillaries are concealed under the 

 skin at its corners. Interiorly there is a conspicuous velum in both 

 jaws. The small nostrils lie in a membranous space above the pre- 

 orbitar. 



The entire head is covered with smooth integument, which has no 

 inflexed folds at the edges of the opercular pieces or preorbitar, but 

 is continuous with single lips, that are capable of covering the jaws. 

 The gill-membrane is continuous with the edges of the interopercula, 

 and passes over the isthmus to which it is partially adherent, leaving 

 a small flap posteriorly. It is sustained by four flat thin rays on each 

 side. In length the head is equal to five diameters and a half of the 

 circular orbit, and the space between the eye and the tip of the gill- 

 flap equals three of these diameters. The eye is near, but does not 

 touch the upper profile of the head. A triangular preorbitar, having 

 a length equal to the diameter of the orbit, is so concealed by the in- 

 tegument that it is scarcely discernible in the recent fish, but in the 

 dried specimen it shows a slightly raised disk bounded in a somewhat 

 radiated manner by slightly prominent mucous canals. The rest of 

 the suborbitar chain goes round more than half the orbit in form of 

 a slender line of simple mucous tubes. The two limbs of the pre- 

 opercidum, eqiial to each other in length, meet at a right angle and 

 inclose a broad and perfectly smooth cheek. In the dried fish the 

 disk of the bone appears raised, and is edged irregularly with mucous 

 prominences, but the under border of the bone is thin, and is scarcely 

 distinguishable from the very thin, flexible interoperculum. At the 

 temporal angle of the gill-plate there originates a bushy cluster of 

 prominent ramifications, which disappear about the middle of the 

 disk, and are most probably not visible at all in the recent fish. The 

 rather narrow, very thin suboperculum is lengthened into the tip of 

 the gill-cover, in which the flexible bone is scarcely to be distinguished 

 from the membrane. The gill-opening is restricted above, the whole 



19* 



