POMACENTRIDAE. 129 
with a faint inner pale band; traces of pearly spots on scaled base of anal and 
on belly and posterior part of body, but none of these spots are present in the 
larger specimens. 
The one specimen from Perico Island is similar in color to the paler forms 
above described; spots on side of head distinct; no spot on caudal peduncle; 
fins same color as body; pale spot in axil of dorsal and anal. 
Comparative Measurements. 
Pomacentrus rectifraenum Pomacentrus gilli. 
Total length 94 mm. 94 mm. 
Head 3.13 3.13 
Depth sae 1.88 
Eye | 3.33 Ah fy 
Preorbital, between eye and corner of mouth 4.28 - 5.42 
Maxillary 3.33 3.15 
Interorbital 2272 3.15 
Gilbert and Starks (loc. cit.), state that P. gilli is closely related to P. 
rectifraenum but differing constantly in the uniformly translucent pectoral, 
larger eye, narrower and flatter interorbital space, narrower preorbital, which is 
serrated to a point opposite to or in advance of the angle of the mouth, and in the 
shorter dorsal and anal fins. 
In the specimens which we have identified as these two species we find that 
all the above characters do not hold. In many of the smaller specimens of P. 
rectifraenum, the pectorals are translucent; the eye is not constantly larger in 
P. gilli; the interorbital space agrees in being narrower in P. gilli, but the differ- 
ence in flatness in the two can not always be distinguished; while in the larger 
specimens the preorbital is somewhat narrower in P. gilli. This character is 
hard to distinguish in the small specimens and the preorbital serrations are 
variable and are of no importance as a means of separating the two species. 
Out of thirty-four specimens of P. rectifraenum we have one specimen in which 
there are 13 rays in the anal; out of fifteen specimens of P. gilli we have one 
with 16 dorsal rays and one with 14 anal rays. These are probably individual 
variations and in general would not effect the separation of the species, since 
this variation does not affect both dorsal and anal in the same specimen. In 
our specimens, the presence of accessory scales upon the top of head and between 
eyes in P. rectifraenum and their absence in P. gilli seems to furnish a distin- 
guishing character, particularly in the larger individuals. Another constant 
and well-marked character in P. rectifraenum is the presence of a very distinct 
