shlfeldt] THE PHYSIOGNOMY OF FISHES 139 



as we find them in typical fish forms in the waters of the globe 

 everywhere. 



When we come to study the heads of other fishes, however, 

 with this simple one in hand, it is truly astonishing to observe 

 the amount of variation that has taken place throughout all the 

 families known to us. There is no structure of this part of the 

 ichthyic economy which has not been powerfully altered in some 

 way or another. Cephalic organs have either been greatly 

 exaggerated, or else entirely suppressed. The skull as a whole 

 in not a few species has become so thoroughly distorted and 

 twisted that, in a few instances, it almost ceases to resemble the 

 head of a fish. Others have remarkable appendages attached to 

 the head, and these are of a great variety of kinds and forms. 

 One group at least, with numbers of its allies near and remote, 

 have the skull turned completely sidewise, with both eyes rotated 

 to one side. Flounders and their congeners well represent these. 



Passing now to a consideration of the profile of the head in 

 various groups of fishes, it may be noted that, in some instances, 

 this configuration has been likened to the fancied resemblance 

 to other animal forms, or even to inanimate objects. As an 

 example of the former, the Sea Horse {Hippocampus hudsonius) 

 may be cited (Fig. 20), the anterior third of its body bearing a 

 certain resemblance in outline to a maneless horse in miniature; 

 while upon the other hand Selene vomer (Fig. 14) has also been 

 called in the vernacular "horse-head," the "moon-fish," and also 

 the "look-down"; there are no end of instances of this kind. 



In many fishes the elongation of either the upper or the lower 

 jaw is, in the adult, a permanent feature of the face, and in not a 

 few instances it has its uses. Such a modification is well exempli- 

 fied in such forms as the Common Paddle-fish (Polyodon spatula) ; 

 in the well-known saw-fish (Fig. 2), and in many others; while 

 in such a species as any one of the Halfbeaks, as Hyporhynchus 

 unifasciatus (Fig. 11) it is only the lower jaw which is unduly 

 prolonged. Occasionally the entire face is thus produced, and a 

 small mouth is present at its distal extremity, as we see it in several 

 species of the so-called Trumpeters, the Spotted Tube-mouth 

 being an interesting example (Fig. 12). 



Appendages of various kinds, some of them having their actual 

 uses, appear on the heads of no end of various species of fishes. 

 These appendicular structures naturally add to the character 

 of the profile of the form possessing them. 



