47 8 TUBE-B LADDERED 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 premaxillse 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 gigas) of the larger rivers of 

 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 Ibs. 

 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. 

 Barrelled The four representatives of the typical genus Osteoglossum may 



Arapaimas. \^ Q 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 barramundi, 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 



