FISHES. 20b 



tlieir culmination in forms that are now so isolated by reason of the loss of interme- 

 diate tyjH's that they are distinguished as peculiar families. Among the Scombrids in 

 question is the genus Acant/ioci/bium, which exhibits, in its elongated spinous dorsal 

 fin, and jjrojecting jaws, as well as the structure of the gills, characters which tend 

 towards the sword-fishes. Another specialized group is that represented by the elon- 

 gated compressed s])ecies in which the spinous dorsal is also elongated, and in which 

 the ventral fins become feeble or obsolescent. These lead naturally to another group 

 of fishes which apparently are worthy of differentiation into two distinct families. 

 First, we may consider the sword-fishes, and afterwards the ribbon-like Scombroidea. 



The Scombroidea with the u])per jaw elongated and condensed into a sword-like 

 weajion have generally been combined in one family, but the differences manifested 

 by the sjtecies are so great as to demand a recognition of two distinct families, the 

 Histiophorida? and the Xijihiidaj. 



The sail-fishes or bill-fishes, constituting the family HiSTioPHOEiDyE, have the body 

 elongated and more or less compressed ; the spinous dorsal fin is very long and jier- 

 sistent, and often greatly devcloj)ed, the spines being elongated, connected by mem- 

 brane, and constituting the sail of the fishermen, and the ventral fins are present in 

 the shape of elongated compressed spines, and generally have one or two axillary 

 rays; but the chief differences are exhibited by the skeleton, prominent among which 

 are the elongated hour-glass-shaped vertebrse, flag-like neural and haniial s]iines, 

 and the well-developed ribs. 

 Two distinct genera are rep- 

 resented in the American seas. 

 The spear-fish or bill-fish, Tcf- 

 rapticrus albidus, is a ft)rni 

 having the dorsal fin low or 



moderatelv developed, and the i-,^ ,,.. ,/ , , , , , ., , 



ventral fins are represented 



only by the S]iines. It is an inhabitant of the American seas as far north as the 

 New England waters in the summer months, and is not rarely taken by those 

 engaged in the sword-fishery. Occasionally, also, they enter into the fish-j)Ounds 

 along the coast. In the trojiical waters, however, the horizon of the species, according 

 to Professor Poey, is at a depth of about a hundred fathoms. It is probal)le, then, 

 that the temperature guides their movements, and that it is an inhabitant rather of 

 the cooler waters than of the true trojiical ones. It is noted for its antagonism to 

 sharks, and the fish is said to become furious at their appearance, and to engage in 

 violent comliats with them. 



The sail-fish, IIistioi>horus americcnius, is scarcely distinct from the // (/ladiicn, 

 but is distinguished from the Tetraptitrihy the greatly elevated spinous dorsal fin, and 

 by the development of two or three rays within the axils of the ventral spines. This 

 species is also a summer inhabitant of the American waters as far north as New Eng- 

 land, and is likewise occasionally taken by the fishermen. It is, however, so active in 

 its movements that its value scarcely compensates for its capture. 



The true sword-fish is the only representative of the family Xipiiiid^. The body 

 is shorter, much stouter, and less compressed than in the Ilistiophoridas, the spin- 

 ous dorsal becomes atrophied behind, the posterior spines being scarcely visible, 

 and ventrals are entirely wanting. But it is more especially distinguished by the 

 larger short vertebra;, the spiniform neural and hsemal spines, and the development 



