Fishes of the Western North Atlantic 357 



specimens, seen by us at Woods Hole, have been dark brownish above, the tail black 

 from spine rearward, the lower surface white and without dark edgings. 



Relationship to Extralimital Species. Some authors** have considered D. centroura of 

 the western Atlantic identical with D.aspera (Cuvier) 1817'° of the Mediterranean, 

 Madeira, and tropical West Africa," and the two forms do resemble one another 

 closely in general form of disc, in dermal armature (especially thorniness of the tails 

 of adults) and in the narrowness of the lower tailfold combined with the absence of an 

 upper tailfold. However, final decision as to their exact relationship will require com- 

 parison of adult specimens from the two sides of the ocean. Awaiting this, it seems 

 best to recognize both species of the pair, especially since the two appear to be charac- 

 teristic of rather different thermal zones, D. aspera of the tropical-subtropical regions, 

 Z). centroura of warm-temperate regions. 



Size. Apparently D. centroura does not become sexually mature until it attains a 

 breadth of four feet or more, for the claspers extend only a little beyond the tips of the 

 pelvic fins in a male of about 41 inches, and they were not much more developed in 

 one of c^() inches that we have examined. Thus it appears that the great majority of 

 specimens that have been studied, i. e., up to 40—56 inches wide, have been immature." 

 When fully grown this appears to be the largest of the Sting Rays of the western North 

 Atlantic. The maximum width definitely recorded for a specimen certainly of this 

 species, is five feet." The greatest measured length, so far as we can learn, is 10 feet 

 3 inches.'^ But it is certain that some reach a considerably larger size, for a New Jersey 

 specimen has been described as nearly seven feet across,'^ which, if its tail were nearly 

 complete, would have been 13-14 feet long. Thus it rivals in size the giant Sting Ray 

 of Australia and New Zealand {Dasyatis brevicaudata [Hutton] 1875), which has been 

 characterized as "the largest stingaree in the world.""* 



The size at birth is not known. The smallest specimens that can be referred with 

 full confidence to D. centroura are one about 17V2 inches broad, reported many years 

 ago," and another 15^/4 inches broad, taken at Woods Hole during the summer of 

 1946 (see Study Material, p. 352). 



Specimens taken at Woods Hole weighed about 16—22 pounds at a breadth of 

 24—26 inches; 26—40 pounds at 30—32 inches; 45—55 pounds at 34—36 inches; 65—75 



69. Notably Garman, Mem. Harv. Mus. comp. Zool., j6, 1913: 382. 



70. See Rey (Fauna Iberica, Feces, i, 1928: 626) for a good account and illustration of a young specimen of Z). aspera; 

 Doderlein (Man. Ittiol. Medit., 2, 1S8 1 : 228, as Trygon thalassia) for an early history of the species and an extensive 

 list of references, including pre-Linnean ones; Vinciguerra (Ann. Mus. Stor. nat. Geneva, 57, 1923: 76) for dis- 

 cussion of the validity of D. thalassia (MilUer and Henle) 1841, leading to the conclusion that it is not a distinct 

 species. 



71. For list of West African localities and references, see Fowler (Bull. Amer. Mus. nat. Hist., yo [i], 1936: 126). 



72. Gravid females only two feet wide, reported from New Jersey under the specific name D. centrourus by Moore 

 (Bull. U. S. Fish Comm., 12, 1894: 358), almost certainly belonged to some other species of Sting Ray. 



73. Fowler, Rep. N.J. Mus. (1905), 1906: 76. 



74. For one specimen, the breadth of which was not recorded (Garman, Bull. U. S. nat. Mus., 16, 1883: 67), and for 

 another only 42 inches broad, the tip of whose tail was missing, caught io Sandy Hook Bay near New York in 1927 

 (Breder, Copeia, 166, 1928: 6). 



75. Fowler, Proc. Acad. nat. Sci. Philad., 80, 1929: 60S. 



76. Whitley, Fish. Aust., i, 1940: zoz, fig. 227. 77. Garman, Bull. U.S. nat. Mus., 16, i88j: 67. 



