1324 Catalogue of Malayan Fishes. [Dec. 



are almost confined to the abdominal surface, meeting at an acute angle 

 on the throat ; they are divided by a thin longitudinal septum, which 

 does not, however, extend as far back as the angle of the gill-openings, 

 and they consequently have the appearance of being single as in the 

 Gen. Symbranckus. A fold, corresponding to the septum, appears on 

 the external surface of the membrane. In the posterior half of each 

 cavity appear three small, but slightly curved bony arches, with minute 

 branchise. The fourth, posterior, arch is entirely hidden by the integu- 

 ments. The branchiostegous rays are generally short, but unequal : 

 the four upper ones are placed closely together, the two lower ones at 

 some distance below the former ; the second upper ray and the two 

 lower ones are of nearly equal length, about double that of the re- 

 maining three. A linear groove marks the lateral line, which continues 

 nearly in the middle of the side to the point of the tail. In specimens 

 preserved in spirits of wine the contraction of the muscles produces 

 another linear groove dividing the space between the back and the 

 lateral line. All the preceding characters correspond to those of 

 Monoptere javanais, Lacepede. The following are the characters which 

 vary, not only according to age, but even in individuals of equal dimen- 

 sions. The length of the head (measured from the snout to the hinder 

 angles of the gill-openings,) varies from T * T of, to 15^ times in the total ; 

 the tail from ^ of to 2f in the total length. Generally the head is 

 proportionally shorter in the young, but the tail longer than in the 

 adult. The distance between the eyes, across the forehead, is anteriorly 

 about three-, posteriorly about four diameters of the eye. On the top 

 of the head, on the upper lip and the throat appear some minute dis- 

 tant pores, the number of which varies individually. Of the three 

 united fins the two are entirely membranous ; the very small caudal 

 encloses from two to five undivided rays, so very minute, that a lens 

 is required to observe them through the semitransparent membrane. 

 In adult individuals they are frequently not distinguishable. The dor- 

 sal commences a little behind the root of the tail, rising into a low arch 

 above the middle of the tail and then gradually decreasing towards the 

 caudal. The anal may be traced from the anus in the form of a raised 

 line, sunk in a groove ; on the posterior two thirds of the tail it forms 

 a skinny hem, less elevated than the dorsal. Both are frequently very 

 indistinct in individuals of all ages, and can then barely be distinguished 





