270 PROCEEDINGS OP THE ACADEMY OP 



Head rather elongated and acutely conical, about twice as long as high. 

 Eyes large and elliptical, and very closely approximated. The frontal bones 

 are extremely narrow. 



Mouth oblique. Lower jaw projecting much beyond the upper and furnished 

 with a short compressed and wide flap or barbel in front of the symphisis. 



Villiform teeth present only on the jaws. 



Dorsal fin behind the vertical of the anus, and furnished with simple and 

 articulated rays. Anal fin as long as or longer than the dorsal. 



Myxodagnus operculars Gill. 



The body is highest in front of the dorsal fin, and nearly equals at that 

 place a tenth of the total length ; thence it regularly declines towards the 

 caudal fin, and, behind the dorsal, is less than a third of the height in front. 

 The width at the bases of the pectorals is equal to two-thirds of the greatest 

 height, or 6-100 of the length. 



The head is acutely conical and elongated ; from the tip of the lower jaw to 

 the end of the bony operculum it forms a sixth (17-100) of the entire length ; 

 from the front of the upper jaw to the same place, 16-100. Its greatest height 

 at the vertical of the preopercular margin exceeds a half (9-17) of its length ; 

 that behind the eyes more than a third, (6-17). The profile is nearly straight, 

 but very slightly concave in front of the eyes. The crown is transversely 

 arched and smooth. The width at the preoperculum equals 7-17 of its length ; 

 the width behind the eyes a quarter of the same. The frontal bones between 

 the eyes are exceedingly narrow, so that the orbits appear to be separated by 

 little more than a mere septum. 



The eyes are longitudinally elliptical and of large size. The long diameter 

 of the orbit nearly equals the thickness behind, or quarter of the head's length. 

 The distance between the snout or symphisis of the upper jaw and the orbit 

 equals three-fourths of a diameter. 



The posterior margin of the preoperculum is much less than the inferior and 

 nearly vertical ; the latter is oblique. The breadth is greatest at the angle. 

 The pores are obsolete. The postorbital or temporal ridge is nearly as long 

 as the diameter of the orbit. 



The opercular fringe is composed of six or seven short filaments. The mem- 

 branous extensions of the subopercular and interopercular bones are moderate 

 and rather stiff. 



The dorsal commences behind the vertical of the anus and the end of the 

 first fourth of the total length, and behind the vertical of the posterior margin 

 of the seventh scale of the lateral line. Its height at the middle equals a half 

 of the greatest height of the body ; there are thirty-six rays, none of which 

 appear to be divided, and the articulation is itself almost obsolete. 



The anal fin commences in front of the dorsal and before the end of the first 

 fourth (23-100) of the length ; about two rays are in advance of the dorsal. 

 The height at the middle equals seven-tenths of the greatest height of the 

 body. There are thirty eight rays, the first two of which appear to be simple, 

 and the rest are simply articulated. 



The caudal fin forms an eighth (12-100) of the total length. It has eight 

 articulated rays forked at its terminal half, two simply articulated rays and 

 two short simple ones. 



The pectoral fins are angulated behind by the extension of the sixth as well 

 as of the fifth and seventh rays. The superior four rapidly increase towards 

 the fifth. The margin of the fin beneath is much curved forwards, the rays 

 rapidly decreasing. The longest ray exceeds a fifth of the total. 



The ventral fins have each three simply articulated and rather stout rays ; 

 the median is longest and equals a third of the pectoral's, or 7-100 of the total 

 length. 



The scales are of moderate size, finely striated concentrically, and arranged 



[Sept. 



