2 9 20 SHARKS AND RAYS 



The typical genus is represented by a small number of existing^ 

 species, two of which are European; one of these, Myliobatis aquila, 

 occasionally visiting the British coasts, where it is often termed the whip ray. In 

 this group the head is free from the disc, and the fin on the muzzle single. The 

 large, flat, hexagonal teeth form a tesselated pavement, highly convex in the upper, 

 but flat in the lower, jaw; the individual teeth are arranged in seven longitudinal 

 rows, those of the unpaired middle row being much elongated and transverse, while 

 the others form less irregular hexagons. The whip-like tail, in addition to a dorsal 

 fin near the root, is generally armed with a large barbed spine about the middle of 

 its length. In the young the middle row of teeth are not larger than the lateral 

 ones, and their relative width continues to increase throughout life. The species 

 above named, which has an almost cosmopolitan distribution, may attain to a length 

 of upward of fifteen feet, with a weight of about eight hundred pounds. When cap- 

 tured, these rays lash out with their tails, and thus inflict severe wounds with the 

 spine. Fossil species of this genus occur through most of the Tertiary strata; and 

 among these one from the Eocene of Egypt is remarkable for its enormous size, the 

 teeth of the middle row being rather more than five inches in width. Although it 

 is difficult to form an estimate of the exact size of the fish to which these teeth be- 

 longed, it is thought that the width of the disc must have been about fifteen feet. 

 Other Genera * n ^ e a ^ e ^ genus Aetobatis, now represented by a single widely- 

 spread tropical species, but common in the Tertiary formations, the 

 muzzle carries two fins, and the dentition comprises only a single series of 

 transversely elongated teeth, corresponding to the central row of the typical genus. 

 In a third genus (Rhinoptera) , of which there are seven living and several Tertiary 

 species, the so-called fins on the muzzle are likewise double, while the tesselated 

 teeth form five or more series. Of these the middle one is the largest, the first, or 

 first and second, lateral series somewhat narrow, and the remainder in the form of 

 more or less nearly regular hexagons; the dental plates of both jaws being strongly 

 arched from back to front. The largest existing members of the family belong to 

 the genera Dicerobatis and Cephaloptera , which are mainly confined to the tropical 

 seas, and to which the name of devilfish might well be restricted. In the former 

 of these the pectoral fins to not extend on to the sides of the head, which is trun- 

 cated in front, and furnished with a pair of forwardly-directed appendages contain- 

 ing fin rays, the nostrils being widely separated. Both jaws contain numerous 

 rows of flat or tuberculated teeth; and the whip-like tail has a single dorsal fin 

 above and between the pelvic pair, and may be armed with a spine. In the second 

 genus, the mouth is terminal, and teeth are present only in the lower jaw. One of 

 the Indian representatives of the first genus is known to measure fully eighteen feet 

 across the disc, and a weight of over one thousand two hundred pounds has been 

 recorded. Sir W. Elliot states that the horn-like appendages ' ' are used by the 

 animal to draw its prey into its mouth, which opens like a huge cavern between 

 them. The fishermen [in India] say they see these creatures swimming slowly along 

 with their mouths open, and flapping these great sails inward, drawing in the 

 smaller crustaceans on which they feed." The capture of such hideous monsters is 

 a work of no little difficulty and danger, as they are quite capable of overturning a 



