PHILIPPINE MACROUROID TFISHES 
GILBERT AND HUBBS. 371 
Sexual dimorphism.—We have been able to demonstrate the ex- 
istence of sexual dimorphism in this family for the first time. In 
certain species of Coelorhynchus (C. velifer and its allies, g. v.) the 
first dorsal, pectoral, and ventral fins are decidedly longer in the 
adult males than in the females or the young males. The wide varia- 
tion’ in the length of the outer ventral ray in the subarctic Cory- 
phaenoides cinereus upon reinvestigation is shown to be due likewise 
to sexual dimorphism: the ray is produced into a long strengthened 
filament in the male. In most species of the family no marked sexual 
variation in the length of the fins is evident. 
Age determinations —We have made a short study of the scales of 
the species of Gadomus, as presented in more detail under the head 
of the four species of that genus here reported on.~ The scales of @. 
denticulatus especially show certain marks which greatly resemble 
the so-called “annuli” of certain littoral fishes, and are probably 
indications of a yearly check in the growth of the fish. These marks 
are very obscure or entirely absent in the species inhabiting the 
greater depths. 
Subspecifie intérgradation.—The intergrading of the geographical 
subspecies of Wymenocephalus striatissimus has been worked out in 
detail. So far as known to us this is the first demonstration of its 
kind among the bathybial fishes. 
Distribution correlated with temperature and depth.—The region 
of the Jolo or Sulu Sea forms a partly inclosed basin connected 
with open waters by narrow and comparatively shallow channels; 
the water of the sea is consequently rendered warm, retaining a 
temperature of more than 49° F. to depths of over 1,000 fathoms. 
Though of comparatively small size, the Philippine faunal sub- 
region, comprising these waters of unusually high temperatures at 
great depths, contains a large proportion of peculiar and frequently 
very distinct species, which have probably been evolved in this region 
of peculiar environmental conditions. The process of their evolu- 
tion has doubtless been aided or hastened by their isolation, more 
or less complete, in this partly inclosed sea.? 
Ill. THE GEOGRAPHICAL DISTRIBUTION OF THE MACROUROID 
FISHES OF THE PHILIPPINE AND ADJACENT ISLANDS. 
There are now known about the East Indian and the Philippine 
Islands no fewer than 75 or 76 species? of the Coryphaenoididae. 
In no other area of similar size is there known a fauna comprising 
such a numerous and varied assemblage of these fishes. 
1 Gilbert and Hubbs, Proc. U. S. Nat. Mus., vol. 51, 1916, p. 107. 
2 Some of the species range northward to southwestern Luzon. 
8 Including the three subspecies of Hymenocephalus striatissimus ; 69 of these species 
were obtained by the Albatross. 
