PHILIPPINE MACROUEOID FISHES GILBERT AND HUBBS. 537 



the sensory canal system and thin bony septa of the head are devel- 

 oped, this species holds a position intermediate between striatisslmus 

 and its allies on the one hand, and longiceps and longipes on the 

 other. The gill-membranes, which are free from the sides of the 

 isthmus, unite, with a free fold, below the posterior margin of the 

 orbit. The gill-rakers are arranged as in other species of the sub- 

 genus Hymenocephalus ; there are two series of 18 on the lower limb 

 of the outer arch; those of the outer series are decidedly, more 

 crowded and smaller than those of the inner series, as they are con- 

 fined to the restricted limits of the first gill-slit, which is only about 

 as long as the orbit. Seven branchiostegals. 



The distance between the anus and the ventral base is equal to the 

 distance from the tip of the snout to the hind margin of the orbit, 



i^3 





Fig. 33. — Hymenocephalus xascexs. Type. 



and about equal to the distance between the ventral base and the fold 

 of the gill-membranes across the isthmus. 



The ventral lens-shaped organs are both round ; the diameter of the 

 posterior of the two, although about twice that of the anterior one, is 

 but one-fourth that of the pupil (half pupil in longiceps and longipes). 



The few large scales retained on the side of the type bear 10 to 16 

 fine sharp spinules, directed backward, and arranged in quincunx 

 order. The lateral line is rather poorly developed; it is separated 

 from the first dorsal base by 2 rows of scales and from the front of 

 the second dorsal by 4 rows. 



No denticulations on the second dorsal spine are apparent. The 

 length of the first dorsal base is contained 1.9 (1.5 to 2.1) times in 

 the interval between the dorsal fins, and 1.2 (1.2 to 1.3) times in the 

 postorbital length of the head. The length of the weak and slender 

 pectoral fin is contained 1.6 (1.6 to 1.9) times in the head; the outer 

 ventral ray, with its filament, 1.25 (1.1 to 1.3) times; the second 

 ventral ray. 2.1 (2.0 to 2.35) times, barely reaching to the anus. 



