=Soft-rayed Fishes.=--Among the _Teleostei_, or bony fishes, those which first appear in geological history are the _Isospondyli_, the allies of the salmon and herring. These have all numerous vertebræ, small in size, and none of them in any notable degree modified or specialized. They abound in the depths of the ocean, but there are comparatively few of them in the tropics. The _Salmonidæ_ which inhabit the rivers and lakes of the northern zones have from 60 to 65 vertebræ. The _Myctophidæ, Stomiatidæ_, and other deep-sea forms have from 40 upwards in the few species in which the number has been counted. The group of _Clupeidæ_ is nearer the primitive stock of _Isospondyli_ than the salmon are. This group is essentially northern in its distribution, but a considerable number of its members are found within the tropics. The common herring (_Clupea harangus_) ranges farther into the arctic regions than any other. Its vertebræ are 56 in number. In the shad (_Alosa sapidissima_), a northern species which ascends the rivers, the same number is recorded. The sprat (_Clupea sprattus_) and sardine (_Sardinia pilchardus_), ranging farther south, have from 48 to 50, while in certain small herrings (_Sardinella_) which are strictly confined to tropical shores the number is but 40. Allied to the herring are the anchovies, mostly tropical. The northernmost species, the common anchovy of Europe (_Engraulis enchrasicolus_), has 46 vertebræ. A tropical species (_Anchovia browni_) has 41. There are, however, a few soft-rayed fishes confined to the tropical seas in which the numbers of vertebræ are still large, an exception to the general rule. Among these are _Albula vulpes_, the bonefish, with 70 vertebræ, _Elops saurus_, the ten-pounder, with 72, the tarpon (_Tarpon atlanticus_), with about 50, and the milkfish, _Chanos chanos_, with 72. In a fossil Eocene herring from the Green River shales (_Diplomystus_) I count 40 vertebræ; in a bass-like fish (_Mioplosus_) from the same locality 24--these being the usual numbers in the present tropical members of these groups. The great family of _Siluridæ_, or catfishes, is represented in all the fresh waters of temperate and tropical America, as well as in the warmer parts of the Old World. One division of the family, containing numerous species, abounds on the sandy shores of the tropical seas. The others are all fresh-water fishes. So far as the vertebræ in the _Siluridæ_ have been examined, no conclusions can be drawn. The vertebræ in the marine species range from 35 to 50; in the North American forms, from 37 to 45; and in the South American fresh-water species, where there is almost every imaginable variation in form and structure, the numbers range from 28 to 50 or more. The _Cyprinidæ_ (carp and minnows), confined to the fresh waters of the northern hemisphere, and their analogues, the _Characinidæ_ of the rivers of South America and Africa, have also numerous vertebræ, 36 to 50 in most cases.