52 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
Subclass TE LEOSTOMI. — The True Fishes. 
Skeleton usually bony, sometimes cartilaginous; skull with sutures; membrane bones (opercle, 
preopercle, etc. ) present; gill-openings a single slit on each side; gills with their outer edges free, their 
bases attached to bony arches, normally 4 pairs of these, the fifth pair being typically modified into tooth- 
bearing lower pharyngeals; median and paired fins developed, the latter with distinct rays; ova small; 
no claspers; heart developed, divided into an auricle, ventricle, and arterial bulb; lungs imperfectly 
developed or degraded to form a swim-bladder, or entirely absent. 
Omitting orders not yet known to be represented in Hawaiian waters we have the following 
analysis of — 
ORDERS OF TRUE FISHES. 
a. Body eel-shaped, provided with very many (100 to 125) vertebra; scales minute or wanting; no ventral fins; gill- 
openings restricted; gill-arches 4 pairs, the hindmost being modified as pharyngeal bones; palato- 
pterygoid arch present; premaxillaries atrophied; maxiilaries lateral, more or less confluent with the 
palatines; shoulder-girdle not attached to skull Apodes, p. 73 
aa. Body not truly eel-shaped; the vertebra usually in moderate or rather large number (14 to 150); ventral fins usually 
present; gill-openings typically ample; premaxillary always present, and maxillary usually so; shoulder- 
girdle near the cranium, usually but not always attached to it; hypercoracoid and hypocoraeoid well 
developed, not coalescent. 
*6. Gill-arches with the bones reduced in number; air-bladder without duct; ventrals abdominal or subabdominal, if 
present; no mesocoracoid. 
c. Gills pectinate; gill-openings large; dorsal and ventral usually with spines Hemibranchii, p. 114 
cc. Gills tufted; gill-openings very small; opercle a simple plate; skin with bony plates Lophobranchii, p. 117 
56. Gill-arches normal. 
d. Ventrals abdominal; pectoral fins inserted low; fins without spines. 
e. Air-bladder, if present, with pneumatic duct; lower pharyngeals separate; anterior vertebra not modified; 
mesocoracoid typically present Isospondyli, p. 52 
ee. Air-bladder without pneumatic duct; lower pharyngeals fully united Synentognathi, p. 121 
dd. Ventral fins usually anterior in position; spines usually present in the fins; pectoral fins not on the plane of the 
abdomen; parietal bones usually separated by the supraoccipital. (Spiny-rayed fishes chiefly.) 
/. Pectoral fins not pediculate, the gill-openings in front of them Acanthopteri, p. 137 
ff._ Pectoral fins pediculate, the basal bones reduced in number and elongate; gills in the axils of the pectorals. 
Pediculati, p. 516 
Order F. ISOSPONBYLI. — The Isospondylous Fishes. 
Soft-rayed fishes with the anterior vertebrae simple, unmodified, and without auditory ossicles; 
symplectic present; no interclavicles; opercular bones distinct; pharyngeal bones simple above and 
below, the lower not falciform; mesocoracoid arch always well developed, as in the Ostariophysi and 
the Ganoidei, forming a bridge from the hypercoracoid to the hypocoraeoid; bones of jaws developed, 
the maxillary broad, always distinct from premaxillary and forming part of margin of upper jaw; no 
barbels; shoulder-girdle well developed and connected with the cranium by a bony post-temporal; 
gills 4, a slit behind the fourth; air-bladder, if present, with a pneumatic duct; dorsal and anal fins 
without true spines; ventral fins abdominal, sometimes wanting; scales usually cycloid, sometimes 
ctenoid, occasionally wanting; no developed photophores; adipose fin present or absent; a large group 
comprising most of the marine soft-rayed fishes, excepting those found in the deep sea, these com- 
posing the degenerate group called Iniomi. Some of the forms, as Elopidse, Albulidse, etc., show 
analogies with the ganoid allies of the Cycloganoidei. This indicates the descent of the Isospondyli 
from a ganoid stock, Amioidei, and from this order or its ancestors doubtless all the bony fishes have 
sprung. 
FAMILIES OF ISOSPONDYLI. 
l. Isospondyli : Mesocoracoid arch developed, the connection of the shoulder-girdle with the cranium perfect. 
a. Dorsal fin inserted more or less before anal (rarely slightly behind it); shore fishes or river fishes, usually silvery in 
coloration and with the skeleton firm; gular plate present, between branches of lower jaw; mouth large; 
teeth present, all pointed; axillary scales and sheaths large Elopidx , p. 53 
aa. Gular plate none. 
5. Lateral line well developed. 
c. Teeth present; no accessory branchial organ; mouth small, horizontal Albulidx , p. 54 
