XVII ELASMOBRANCHII—BATOIDEI 465 
as well as on the adjacent coasts, and specimens have been 
obtained from Lake Munroe at some distance from salt water.’ 
Ellipesurus and Paratrygon are freshwater genera, found in 
Colombia, Venezuela, and Guiana. 
Fossil remains of undoubted Trygonidae appear to be confined 
to the Tertiary period. 
Fam. 7. Myliobatidae (Kagle-Rays)—Disc much broader than 
long, and rhombic in shape. The huge pectoral fins are not 
continued to the extremity of the snout, but cease on the sides 
of the head, and reappear in front of the snout as a pair of 
distinct folds, the so-called cephalic fins. The head projects 
above the level of the disc, and consequently the eyes and 
spiracles are lateral in position. Tail long, slender, and whip- 
like, with a single dorsal fin near the root, and usually one or two 
serrated spines behind the fin. A rectangular naso-frontal fold is 
present. The dentition consists of flat, hexagonal, pavement-like 
erushing teeth arranged from before backward in arched rows in 
both jaws, and there is either a single median row of large teeth, 
with (e.g. Myliobatis) or without (e.g. Aétobatis) the addition of 
several rows of much smaller teeth on each side, or there are 
numerous rows, the teeth then decreasing in size from the middle 
line laterally (e.g. Rhinoptera). Skin smooth. Sexes shnilar. 
Five genera and about twenty-seven species are known; all 
inhabitants of tropical and subtropical seas. 
Myliobatis is represented in the Mediterranean by two species, 
and one of them, the almost cosmopolitan JZ aquila (Fig. 266), 
has been taken at various points on the eastern and southern 
coasts of England. <Aétobatis is also widely distributed in 
tropical seas, but is unknown in European waters. Rhinoptera 
has one species in the Mediterranean, while others have been 
recorded from Brazil, the Atlantic and Pacific coasts of North 
America, and the East Indies. The two tropical genera 
Dicerobatis and Ceratoptera have the cephalic fins prolonged 
anteriorly into a pair of horn-like appendages, which are said 
to be used in conveying food to the mouth. The teeth are 
small, flat or tubercular, and are arranged in numerous rows. In 
Ceratoptera they are wanting in the upper jaw. The Eagle- 
Rays feed principally on Molluscs, the shells of which they 
crush with their large grinding-teeth. Some of them attain 
1 Jordan and Evermann, op. cit. p. 85. 
VOL. VII 2H 
