276 Papers from the Marine Biological Laboratory at Tortugas. 



Jordan and Evermann (1896) say of the eagle rays in general that they 

 have long whiplash tails with a spine behind the dorsal fin, while nothing is 

 said of the spines of Aetobatus narinari. Later, however, Jordan himself, 

 in volume in (1898), says of A. laticeps (Gill), which he believes to be 

 identical with A. narinari, that its anterior caudal spine equals the length 

 of the base of the dorsal, which in turn is half the length of the second 

 spine. This the present writer has found to be true of every 2-spined 

 tail examined. Euphrasen, however, was the first to note this peculiarity. 

 Miranda Ribeiro (1907) says that the filiform tail may have from one to 

 five spines behind the small dorsal, but Gunther (19 10) affirms that one is 

 the rule though there may be more. 



The tail of Aetobatus narinari is always armed with one and ordinarily 

 with two or three spines, while the number may rise to four or five as 

 recorded by Gunther (1870) and as shown in figure 7, plate iv, of my best 

 Bieaufort specimen and of Quoy and Gaimard's plate, which has been pre- 

 V ously described. My notes on the tail structures of Beaufort specimens 

 are not so full as could be wished for, but the following data are given to 

 supplement what has preceded. My first specimen, taken June 12, 1909, 

 had a tail 403^2 inches long, armed with two spines. My second, taken by 

 Coles at Cape Lookout July 3 of the same year, had a tail 353^ inches in 

 length, likewise bearing two spines, the anterior three- fourths of an inch 

 long, the posterior 2}/^ inches. 



During 1910, I examined three fine specimens. The first had a 33-inch 

 tail bearing two spines, the first of which measured i inch, the second 2}/^. 

 Specimen No. 2 possessed a tail 39^^ inches long, bearing only one spine 

 and it but three-fourths of an inch long. This was evidently a regenerating 

 structure, for the faint groove back of the dorsal showed plainly that a 

 spine or spines had been torn out. My best Beaufort specimen for 19 10 

 was No. 3, which came into my hands while yet alive. Its tail bore three 

 spines, the anterior ij^ inches long, the middle one (nearly torn off in the 

 net) 1 34 inches, the posterior 2 inches in length. This torn-off sting had 

 two roots. 



Mr. Coles's (1910) largest spotted ray was 5^ feet wide, 3 feet in length, 

 and had a tail 5^ feet long bearing four spines, but these were unfortunately 

 not measured. Dr. R. E. Coker, when director of the Beaufort Laboratory, 

 recorded in 1901 the capture in the outer harbor of a spotted ray 4 feet wide 

 and 2 feet 2 inches long, with a tail 4 feet 8 inches in length. Tail and 

 spines (which have been excised) are preserved in the museum of the station. 

 The short sting is 2^ inches long and has two short roots. The longer 

 sting measured 4J^ inches and has a blunted single root which bears evidence 

 of having been cut off with a knife. The tail is black and has a slight 

 ventral keel. 



The 4-spined tail, previously referred to and shown in figure 7, plate iv, 

 is, after 2}^ years of drying, 4 feet long. Of its four spines the first is 

 2 inches long, the second (which lacks a fraction of the tip) is 43^ inches, 



