THE CYPRINODONTS 2843 



Unfortunately, there are no fossil forms to aid in the explanation of the peculiar 

 geographical distribution of the family, which is very similar to that of the chro- 

 mids; but there can be little doubt that the ancestral types originally inhabited the 

 great land mass of the Northern Hemisphere, from whence they migrated south- 

 ward to their present isolated distributional areas. It is, however, not a little 

 remarkable that whereas in their migration to Africa they have been accompanied 

 by members of the carp tribe, in tropical America they entirely take the place of 

 that family. The numerous genera, none of which are common to the two Hemis- 

 pheres, are ranged under eleven groups or subfamilies, the majority of which are 

 confined to either the one or the other half of the distributional area, although a 

 few have representatives of both. As regards their habits, some of these fishes are 

 strictly carnivorous, while others are as exclusively vegetable feeders. 



The figured species belongs to the last subfamily, which includes four exclu- 

 sively American genera, represented by some forty species, and characterized by the 

 somewhat elongated dorsal fin, behind which is a small fatty fin; by the gill 

 membranes being free from the isthmus, and also by the distinct serration of the 

 middle line of the under surface of the body. 



On account of their large size, two other genera of these fishes, which have 

 respectively received the names of Hydrocyon and Cynodon, must be mentioned; 

 the former being from tropical Africa, and the latter from Brazil and the Guianas. 

 They grow to the length of four feet, and are highly predacious; the subfamily to 

 which they belong being characterized by the presence of a short dorsal and anal 

 fin, the large conical teeth, the want of attachment between the gill membranes and 

 the isthmus, and the approximation of the nostrils. 



THE CYPRINODONTS Family CTPRINODONTID^ 



The small fishes which, for want of an English title, we may designate cyprino- 

 donts, bring us to the first family of another sectional group termed the Hap- 

 lomi, which also includes the pikes. In addition to certain other structural 

 features of the skeleton, this group is characterized by the first four vertebrae being 

 separate and of normal form; while in the skull the parietal bones are separated 

 by the supraoccipital, all the opercular bones are present, and the pharyngeals are 

 distinct, the upper ones being directed forward, and three or four in number. As 

 a family, the cyprinodonts are specially distinguished by the margin of the upper 

 jaw being constituted solely by the premaxillae, and the enlargement of the third 

 upper pharyngeal bone. Externally they ma}' be readily distinguished from the 

 carps by the head being scaled as well as the body, and they have no barbels. Both 

 jaws are toothed, and the pharyngeals are also furnished with teeth, which are 

 heart shaped. There is no fatty fin, and the dorsal is situated in the hinder half 

 of the body. The air bladder is simple, and the false gills are wanting. Inhabiting 

 either fresh, brackish, or salt water, these fish are distributed over the south of 

 Europe, Africa, Asia, and America; some being purely carnivorous, while others 

 feed on the organic substances to be found in mud. Most of the forms are 



