478 
TUBE-BLADDERED GROUP. 
are fully as interesting as the latter from their geographical distribution, 
which presents a curious general similarity to that of the existing lung-fishes, 
although in the present instance one of the genera has a much wider range than 
either of the lung-fishes. In confirmation of the northern origin of the present 
group, it is noteworthy that an arapaima exists in Sumatra, and also that an extinct 
genus ( Dapedoglossus ) occurs in the Eocene strata of the United States. From the 
preceding the more typical representatives of this family are structurally dis¬ 
tinguished by the upper pharyngeal bones being three, instead of only two in number. 
Externally these fishes have the body covered with large, hard scales of a mosaic-like 
structure; the lateral line being formed by wide openings of the mucus-canal; and 
the scaleless head nearly covered with roughened ossifications of the skin. The 
margin of the upper jaw is formed both by the premaxi Ike and maxillae, the gill- 
openings are wide, and false gills are wanting. The long dorsal closely resembles 
the anal fin, over which it is placed in the caudal region of the body; both coming 
very close to the tail-fin, with which they may unite as an abnormality. In 
structure the air-bladder may be either simple or divided into cells. 
The true arapaima (Arapaima qiqas) of the larger rivers of 
ArctpctiiUci ^ ^ u tj / o 
Brazil and the Guianas, which is the sole representative of its genus, 
occupies the proud position of being the largest fresh-water bony fish, its length 
not unfrequently exceeding 15 feet, while its weight may reach upwards of 400 lbs. 
As a genus, it is distinguished by the broad cleft of the mouth, in which the lower 
jaw is very prominent, and the absence of barbels, as well as by the rounded lower 
surface of the body, and the moderate length of the pectoral fins. In addition to 
an outer series of small conical teeth in the margins of the jaws, there are rows of 
rasp-like teeth not only on all the bones of the palate, but likewise on the tongue 
and hyoid bones. In spite of its enormous dimensions, the arapaima is captured 
by the natives of Brazil with a hook and line; its flesh being highly esteemed as 
food, and in a salted condition largely exported. It is also taken by being struck 
with an arrow, to which a line is attached; and a graphic account of this method 
of hunting is given by Schomburgk. It appears that a party go out in a boat, 
and row about until a fish is sighted, when the bow and arrow are brought 
into requisition, and if the shot be successful, the monster is at length landed. 
Barbeiied The four representatives of the typical genus Osteoglossum may 
Arapaimas. ]-> e distinguished from the last by the presence of a pair of barbels to 
the lower jaw, the obliquity of the cleft of the mouth, the sharp lower surface of 
the body, and the greater length of the pectoral fins. Of the four species the first 
is American, and has the same distribution as the true arapaima, the second occurs 
in Sumatra and Borneo, while the other two are Australian. The two latter have, 
however, but a very local distribution, the one (0. leichardti) being confined to the 
rivers of Queensland, where it is known to the natives as the barranmndi, and to 
the colonists as the Dawson River salmon; while the second (0. jardinei), which 
is distinguished by the absence of a spine to the anal fin, inhabits the rivers dis¬ 
charging into the Gulf of Carpentaria. The flesh of both these species is highly 
esteemed as an article of food. 
Small-Mouthed The third genus of the family, which includes only a single 
Arapaima. species {Heterotis nilotica), differs from both the foregoing in having 
