32 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
CHARACTER OF THE HAWAIIAN FISH FAUNA. 
The fish fauna of the shores of the Hawaiian Islands is frankly and entirely 
tropical, all the species belonging to genera characteristic of the tropical Pacific; but 
while the families and genera are those of the South Seas, the species are in a large 
degree distinct from the species of Samoa and Tahiti. This fact is evidently con- 
nected with the relative isolation of this group as compared with Polynesia, which 
is connected with the East Indies b} T an almost continuous chain of islands and atolls. 
It is perhaps true that the isolation of Hawaii is due in part to the direction of 
the marine currents. These do not much influence free-swimming fishes like the 
mackerels, but they may serve to transport young fishes from one place to another. 
It is known that the young of shore fishes are often borne out to deep water, so that 
each island becomes the center of a “sphere of influence” so far as its species are con- 
cerned. Many young fishes are borne along in the Gulf Stream of our Atlantic coast 
and in the corresponding Kuro Shiwo of Japan. It is likely that the currents of the 
eastern central Pacific have a similar influence. 
One of these currents, originating to the northward of the Philippines, passes 
eastward between Melanesia and Micronesia, thence along the north shores of Fiji, 
Tonga, Samoa, and Tahiti. Approaching the shores of America, it turns to the 
northward, touching the Revillagigedo and other offshore islands, leaving there a few 
Polynesian species, then returns westward via Hawaii toward the shores of Japan. 
This current may help to give the Polynesian Islands their identical fauna. Since 
it is inadequate to carry these species to Hawaii, the long separation of these latter 
islands has given them a fauna practically distinct, although made up entirely of 
tropical elements. What these elements are is shown in the following table: 
Total number of species of shore fishes found in Hawaii 441 
Number of species confined to Hawaii 232 
Number of species common to Hawaii and Polynesia (Samoa, Tahiti, Fiji) 142 
Number of species common to Hawaii and Japan 53 
Number of species common to Hawaii and Mexico 34 
ANALYSIS OF THE CLASSES OF FISH-LIKE VERTEB RATES. « 
n. Acraniata: Anterior end of the central nervous axis not dilated into a brain and not surrounded by a protective capsule 
or skull. 
b. Notochord perfect, persistent, extending throughout the body, included in a membranous sheath, as is the cord-like • 
nervous axis above it; body elongate, lanceolate, not worm-like, nor enveloped in a tunic; walls of the body 
with muscular myotonies; middle line of body with rudimentary fins; no proboscis; the mouth slit-like, fringed 
with cirri; heart a longitudinal tubular vessel giving off branchial tubes which unite in an aorta; gill-slits 
inclosed externally by a fold in the integument, which incloses a chamber (atrium), which opens below; vent 
remote from mouth Leptocardii, I. 
act. Oraniata: Anterior end of nervous axis dilated into a brain, which is contained within a protective capsule, the 
skull; notochord not continued forward beyond the pituitary body; heart developed and divided at least into 
two parts. 
c. Skull well developed and with jaws; shoulder-girdle and pelvis more or less developed; nostrils not median; gills 
not purse-shaped; limbs, if present, developed as rayed fins, never with fingers and toes like those of the higher 
vertebrates; gills persistent through life Pisces, II. 
Class I. EEETOCtVXvJDII.— T he Eancelets. 
Skeleton membrano-cartilaginous; notochord persistent and extending to the anterior end of the 
head, inclosed in a membranous sheath as is the cord-like axis above it; heart a longitudinal tubular 
vessel giving off branchial vessels which unite in an aorta; end of the nervous axis not dilated into a 
brain, and not surrounded by a protective capsule or skull; blood colorless; respiratory cavity confluent 
a In Ibis, as well as in all other analytic keys in this work, only the Hawaiian fish-fauna is considered. 
