IDIACANTIIUS ANTROSTOMUS. 281 



the top of the snout, midway from the eye to the end of the snout. Four 

 gills, a slit behind the fourth ; gill openings very wide, extending from the 

 upper angle of the operculum down and forward to below the eye. Twelve 

 short branchiostegal rays. Barbel one length of the eye from the end of 

 the chin, twice as long as the head ; outer fourth of the length expanded 

 into a leaf-like organ with a long point at each end, a fleshy and rather 

 thick median portion and a thin transparent border. A light organ closely 

 resembling the eye in external appearance, of half the ocular length, lies 

 above the middle of the upper jaw close behind a vertical from the hind 

 border of the orbit ; a series of twelve similar very small organs is situated 

 at the bases of the branchiostegal rays ; at each side of the isthmus there 

 is a row of ten of these organs ; between the isthmus and the ventrals at 

 each side of the median line of the belly there is a series of thirty-five and 

 a little above them on each flank a parallel series ; the four series continue 

 backward and between ventrals and anal have twenty organs eoch, while 

 along the side of the base of the anal there are about thirty-five more. 

 Below the large organ on the cheek on the upper jaw there is a yellow 

 glandular streak as long as the orbit; similar patches of glandular structiu'es 

 form three longitudinal series of blotches along the flanks, the lower of 

 which lie between the light organs ; jwsteriorly along the bases of dorsal 

 and anal this structure becomes more or less continuous. A prominent anal 

 papilla. Vent below the twenty-seventh i-ay of the dorsal. 



Dorsal and anal separated from the short rays of the caudal by less than 

 the orbital length ; from the snout to the first ray of the dorsal nearly four 

 and to the same ray of the anal more than eight lengths of the head ; anal 

 fin entirely within the hindmost third of the entire length ; fin rays ante- 

 riorly partly free, short, slender, spinous, unsegmented, but near the caudal 

 becoming stouter, longer, more than twice as long as the eye, and seg- 

 mented. At each side of the base of each ray the interne urals and inter- 

 hajmals bear a short rigid spine directed out in such a way that the two series, 

 on the opposite sides of the fin, form a trough or cradle in which the rays 

 lie and are protected when folded back. In the description of Idlacantlws 

 ferox it is said "Each ray starts behind a minute curved spine-like projection 

 of the vertebra." The structure thus described would interfere seriously in 

 folding back the rays. Since the rnys are articulated to the bones bearing 

 the spines in question they would according to the statement quoted articu- 

 late directly with the vertebra). Instead of this, however, it is probable the 



