FISHES. 181 



head) ; on the whole they have some resemblance to mullets. The dorsal fin is long, 

 and without spines, and the veutrals are thoracic and have six rays, the first of which 

 is simple but articulated towards its end ; rarely are they wanting. A further note- 

 worthy feature is the development of a cavity over the gill-chamber, lined with a thick 

 membrane, and which is subservient to the respiratory function and co-ordinate with their 

 peculiar habits. In fact, these fishes not only breathe air direct, but, if deprived of the 

 opportunity to do so, die of asphyxia. They live some in rivers, selecting holes which 

 are to be found along the banks, othei-s in the reservoirs of water known in India as 

 ' tanks,' and " delight in lying in the grassy edges, where the water is only sufficiently 

 deep to cover them, so that they have no difficulty in respiring atmospheric air direct." 

 They are monogamous, and prepare a sort of a nest for the future progeny, the male 

 assuming the task of nest-building, and chiefly using therefor his tail, but " biting off 

 the ends of the reeds that grow in the water." According to Dr. Day, they bi-eed 

 twice a year — about June and December. The male is the chief guardian of the nest, 

 but the female may take up the duty if perchance her mate is lost and she left. In the 

 dry season the fishes burrow in the mud, often to a depth of two feet, or even more. 

 Occasionally they go out on the land, and, thus seen, have received the name of 

 " walking-fish." The Chinese name, " langya," or " living-fish," is due, says Sir John 

 Richardson, to the fact that they are "carried about in tubs, and sold in pieces cut 

 from the fish when alive." Some reach a considerable size, Ophiocephalus marulius, 

 according to Day, " attaining as much as four feet in length." Between twenty-five 

 and thirty species of the family are known. 



Sub-Order VIII. — Acanthopterygii. 



We have next to deal with numerous fishes which agree in having a greater or less 

 number of spines developed on the back, sometimes segregated in a distinct first 

 dorsal, at others in the anterior portion of a single fin, in which case the posterior rays 

 are generally branched. The anal has .also usually two or three spines, —sometimes 

 more, but rarely less than two. The ventral fins are inserted forwards, under or 

 nearly under the pectoral, or sometimes considerably in advance of them, and the 

 external rays are generally spinous. The forms so distinguished have usually been 

 combined together in an order, or sub-order, called Acanthopterygii, or Acanthopteri ; 

 but the group is not a homogeneous one, and it is probable that when the various 

 types shall have been dissected, and critically and comparatively studied, it will be 

 found that several sub-orders will require to be recognized. 



The first group which a])])ears to demand our attention is composed of certain 

 forms, some of which have a long geological history, and which have been generally 

 combined in one family under the name Berycid;e. The diversities between the 

 various representatives of the group are, howevei', considerable ; and it seems to be 

 rather a su])er-family, BERYCOIDEA, with several families. Only one is of sufficient 

 general interest to detain us. 



Under the names of squirrel-fish or Welshman, certain fishes, with the scales 

 smooth on the surface but spinous on the margin, with the bones of the head more or 

 less armed with ridges and .s]>ines, and whose color is generally of a reddish tinge, are 

 jiopularly known to the English settlers in tropical countries, and especially in Florida, 

 Bermuda, and the West Indies ; these form the family Holocenteid Ji. The form is 

 oblong, the head pointed, and the caudal is deeply emarginated, and has pointed lobes 



