47° 



TUBE-BLADDERED GR O UP. 



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 forwards, 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 premaxillge, and the enlargement of the third 

 upper pharyngeal bone. Externally they may 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 

 viviparous ; and the males, which are much inferior in size to the females, and, 

 according to Dr. Giinther, probably the smallest living fishes, frequently have the 

 anal fin specially modified to aid in the reproductive process. As a rule, the fins are 

 relatively larger in the males than in the females, and there is likewise some 

 difference in the coloration of the two sexes. In a fossil state, remains of the 



typical genus occur in the Miocene strata of the 

 Continent, which have also yielded others re- 

 ferred to an existing American genus ; while 

 the head of a species much, larger than any now 

 living has been described from the Pliocene of 

 India, this specimen being figured in the accom- 

 panying illustration in order to show the scales 

 on the head so characteristic of the family. 

 Cyprinodonts are represented by about a score 

 of genera, which may be divided into two sub- 

 families, according to the nature of the food. 

 In the first of these, which includes the typical 

 genus Cyprinodon, and has a distribution co- 

 extensive with that of the family, all the forms 

 are carnivorous or insectivorous, and are char- 

 acterised by the firm union of the two branches 

 of the lower jaw in front, and likewise by the shortness, or slight convolution 

 of the intestines. On the other hand, in the second subfamily, which is exclusive^ 

 restricted to Tropical America, the species seek their food in mud, and have the 

 two branches of the lower jaw but loosely joined together, while the intestine is 

 highly convoluted. It is in this group that the sexual differences are most strongly 

 marked. 



As an example of the family we take a remarkable genus 

 belonging to the first subfamily, represented by three species from 

 Tropical America, one of which (Anableps tetropthalmus) is shown in the accom- 

 panying illustration. Having a broad and depressed head, with the region over the 

 eyes much raised, the elongate body compressed in front and depressed behind, a 

 protractile muzzle, and the cleft of the mouth horizontal and of moderate size, these 



HEAD OF A FOSSIL CYPRINODONT, WITH 

 ONE OF THE SCALES ENLARGED. 



Double-Eyes. 



