The Spotted Eagle Ray. 279 



by numerous narrow grooves, or indented lines, mostly convex forward, 

 somewhat irregular in position and direction, and not corresponding on the 

 two sides. In the type they follow at an average interval of about 10 mm." 

 See also Gilbert and Starks (1904). This marking may be a family character. 

 It certainly is a curious phenomenon and worthy of further investigation. 



The tail of the spotted eagle ray is long, slender, whip-like, and behind 

 the region of the spines is dark in color and often a velvety black. In life it 

 is rounded or but slightly flattened, but dried or preserved specimens, which 

 have been hardened or shrunk by the preservative, are, as previously noted, 

 triangular in cross-section in the region of the dorsal fin and spines, while 

 further back they are rather rectangular in shape with the dorsi-ventral 

 axis about twice as long as the horizontal one. The dorsal and ventral 

 surfaces in dried specimens are slightly curved outward, while the sides are 

 often insunken. At the hinder part of the dorsal flattening, immediately 

 under the spines, there is a (slight) cavity as first noted by Sloane (1725) 

 and by no one else. However, in none of the specimens examined by the 

 writer is it large enough to receive even the one spine immediately over it, 

 much less the whole collection, as Sloane thought. His idea that the ray 

 thus concealed the spines lest they should be an impediment while swimming 

 has of course no foundation. See his statement on page 274. 



The ventrally directed apex of the triangular cross-section of the base 

 of the tail forms a kind of keel. This keel extends backward on the ventral 

 side of the tail for a considerable distance as a fairly distinct body, but 

 nothing of the kind has been found on the dorsal surface. The tail of Dr. 

 Coker's specimen, elsewhere referred to, is black and shows a slight ventral 

 keel. This fact has, I believe, not been recorded before. 



In the largest Key West specimen the apex of the triangle forms a 

 plainly marked keel on the ventral surface of the root of the tail. This 

 extends in the dried tail in diminishing size backward as far as the tip of 

 the last spine. In this same dried tail on the ventral surface, about the 

 middle of its length, is a very small but plainly perceptible keel. This, 

 however, may possibly be the result of desiccation. In none of these 

 specimens is the tail finned, though we may expect to find an embryonic 

 finfold in the tail of the larval forms. 



The table on page 261 records the lengths of the body and tail, absolutely 

 and in relation to each other, for every specimen for which measurements 

 have been given. Ordinarily the tail is said to be 23^ or 3 to 4 times the 

 length of the body (Jordan and Evermann, 1896, and Smith, 1907). The 

 extremes are that the length of tail varies from i to 6.2 times body length, 

 the average being 2.9 for 28 specimens, counting in these wide variants. 

 Excluding the extremes, the average tail is 2.7 times the average body in 

 length in 26 specimens. The wide variations recorded in this table are 

 easily explained as follows. It is rather unusual to find a specimen other 

 than a young one with a perfect tail, and the larger and older an eagle ray 

 is the more likely is it to have suffered mutilation in its caudal appendage. 

 Mr. Coles assures me that such has been his experience. 



