138 NATURE-STUDY REVIEW [14:4— April, 1918 



With this in mind, and confining ourselves to the consideration 

 of the facial features and what they may indicate, 'it may be 

 pointed out that there are two principal views that can be taken 

 of a face — the view en face and the view en profile. 



Passing for the moment to the great fish group or Pisces, we 

 find that representatives of every group in the system, up to 

 include mammals, all possess a facial part of the head, which 

 is very different when viewed en face from en profile. In all the 

 groups below mammals, however, there is little or no variation 

 in the facial expression, beyond what the eyes often expresses 

 associated with what the mouth is capable of expressing. This 

 is due to the fact that there is, in all these forms, an almost com- 

 plete absence of anything approaching muscular play and flexibility 

 of such facial muscles as may be present in these types. 



In considering fishes, it is proposed here to ignore their phy- 

 siognomy as viewed en face, although being, in nearly all instances, 

 most important and interesting, and confine our observations 

 to the marvelous variations that are to be seen when we come to 

 compare the 12,000 or 13,000 fishes of the world now known to 

 science, en profile. 



A very large number, if not the majority of fishes of the world's 

 ichthyfauna, present, upon the side view of the head, an outline, 

 with its included features, that may be referred to a common 

 type. Average examples of this may be seen in our common 

 black bass, in the perch, and in the various species of sunfishes 

 of the American rivers and streams. It is, to all intents, triangular 

 in shape, the base of the triangle being represented by the line 

 joining the first vertebra of the spine and the point immediately 

 below it in the ventral region, the mouth being in the anterior 

 angle. Sometimes the head is very deep, in which case this 

 angle is very obtuse; while in other species the head is more or 

 less narrow from above, downwards, and as a consequence this 

 anterior angle becomes, to a greater or less degree, acute. Further, 

 in the generalized head to which reference is made, the eye is of 

 moderate size, the gape rarely being carried posterior to that organ. 

 All the bones found in the side of the head are here, too, of the 

 simplest form, and as they occur in the group generally. No 

 unusual spines or other appendages are to be met with projecting 

 from any of these bones, — indeed, all the other structures and 

 characters are similarly presented in their greatest simplicity, 



