18 CALIFOKNIA ACADEMY OF SCIENCES 



Material is not at hand to decide the relation between D. longa and D. 

 dipterura. The specimen listed by Jordan (1895 b, \). 389) from Mazatlan may be 

 the latter, if the two species are distinct. In one of the Mazatlan specimens, with 

 the disk 32 cm. long, the upper surface is naked, excei:)t three small spines on middle 

 line near shoulder-girdle. The tail is also naked, and possesses, in addition to the 

 very high cutaneous fold below, a free upper fin-fold half the height of the lower. 

 It is probable that the two species are distinct. 



25. Pteroplatea crebripunctata {Peters). 



. Three specimens seen at Panama. 



The propoi'tions of disk are not essentially different in P. crebripunctata, 

 P. rava, and P. maclura. In all, the distance from tip of snout to front of anal slit 

 equals half the width of the disk (or a little less than half in P. rava); and the 

 extreme length of disk, from tip of snout to hinder margin of pectorals, is contained 

 If to 11 times in the width. A line joining angles of disk intersects very slightly 

 in advance of its middle a line from tip of snout to tip of tail. 



P. crehripancinta and P. maclura are extremely close, differing principally in 

 color, the marblings and spots being finer in P. maclura, and the lighter markings 

 brighter in color, more sharply contrasting with (he rest. P. rava has a sharper 

 snout than the others, the rostral angle being, however, in excess of a right angle 

 (110 degrees). The type of P. rava is a male specimen, 29 cm. long, with well 

 developed claspers and no trace of caudal spine. 



Family MYLIOBATID^. 

 26. Aetobatus narinari (Euphrasen). 



Frequently seen; three specimens preserved, one of which has measurements 

 as given below. 



Rostro-frontal fontanel narrowing anteriorly to opposite the hinder margin of 

 eyes, then abruptly expanding; its greatest width anteriorly, 21 mm.; least width at the 

 constriction, 13 mm.; greatest width posteriorly, opposite middle of spiracles, 18 mm. 



lltOl. 



Tip of snout to front of anus 323 



Tip of snout to posterior margin of pectorals 365 



Width of disk 615 



Length of tail (broken) 1200 



Greatest breadth of head (at anterior origin of pectorals) 106 



Width at eyes (including the latter) 87 



Width of cranium opposite middle of eyes 53 



Width of snout opposite front of eyes 56 



Length of spiracle 31 



Tip of snout to middle of nasal fla]) 61 



Width of mouth 44 



Diameter of iris 11 



The Panama specimens agree entirely with those described by Jordan (1895 

 b, p. 391). The comparative measurements given in the paper cited are often 



