456 TUBE-BLADDERED GROUP. 



In the armoured cat-fish, forming the genus Loricaria, the body is remarkable for 

 its elongated and slender form ; while the head is depressed, with a more or less 

 produced and spatulate snout, on the under surface of which the mouth is situated 

 at a considerable distance from the extremity, its margins being surrounded by 

 large folds, and each corner having a barbel. Both the dorsal and anal fins are 

 short and elevated, and the entire head and body enveloped in a bony cuirass. 



SECTION PLECTISPONDYLI. 

 THE CARP TRIBE, Family CYPRINID^:. 



Adopting a modification of Professor Cope's classification, the eels and their 

 allies may be regarded as forming one sectional group of the suborder, while the 

 cat-fishes constitute a second by themselves. A third equivalent group will then 

 be made by the carps, together with the under-mentioned family of the characinoids 

 and certain allied forms. This third group for which the name Plectispondyli has 

 been proposed while agreeing with the cat-fishes (forming the group Nematognathi) 

 in having the first four vertebra fused together and highly modified, differs in the 

 presence of a subopercular bone. As in the last family, the margin of the upper 

 jaw is formed by the premaxilla3, and the whole mouth is toothless, teeth being- 

 developed on the pharyngeal bones alone. While the head is invariably naked, the 

 body is generally covered with scales, and although it may be scaleless it is never 

 invested with bony plates. False gills may be developed, and, if so, are glandular. 

 When an air-bladder is present, it is always of large size ; and it may be divided 

 into two lateral moieties enclosed in an ossified capsule, or constricted into an 

 anterior and posterior portion which are not thus protected. The numerous 

 members of this family are fresh-water fish, confined to the Old World and North 

 America, being quite unknown in the southern half of the New World, and also in 

 Australia. Showing much less diversity of form and habits than the cat-fishes, 

 the carp tribe are for the most part omnivorous, although a few of its members 

 restrict themselves to a vegetable diet. Although some of them prefer muddy 

 situations, where their barbels are probably of assistance, the majority of the carps 

 differ from the cat-fish in selecting clear waters for their haunts. The Indian 

 forms seem to be more carnivorous than their European relatives, many of the 

 larger kinds preying upon their smaller brethren. Geologically, the carps appear 

 to be a comparatively modern group, the earliest known forms occurring in the 

 Eocene of Sumatra ; these being identified with existing Oriental genera. Other 

 fossil carps have been obtained from the North American Eocene, and are assigned 

 to extinct generic types ; while in the Continental Miocene we find representatives 

 of a number of the existing European genera, as well as of a few now mainly or 

 exclusively Asiatic. On account of their more cleanly feeding-habits the flesh of 

 the carps is superior to that of the cat-fishes. The family is represented by over 

 a hundred existing genera, arranged under two subfamilies. 



,_ The common carp (Cyprinus carpio) claims our attention as the 



typical representative of the subfamily Cyprinince, characterised by 



the air-bladder (wanting in one Oriental genus) not being enclosed in bone, and 



divided into an anterior and posterior moiety. In the Oriental genus (Homalop- 



