X8 CALIFORNIA ACADEMY OF SCIENCES 



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

 dipterura. The sjiecimen listed by Jordan (1895 b,]). 389) from Mazathm 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, except 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 lialf the height of the lower. 

 It is probable that the two species are distinct. 



25. Pteroplatea crebripunctata [Paters). 



Three specimens seen at Panama. 



The projiortions of disk are not essentially different in P. cynltripunctata, 

 P. rava, and P. maciura. In all, the distance from ti]) of snout to front of anal slit 

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

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

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

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



P. crebripunctata and P. maciura are extremely close, differing principally in 

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

 brighter in color, more sharjily contrasting with the rest. P. rava has a shar2:)er 

 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.E. 

 26. Aetobatus narinari {Euphvasen). 



Frequently seen; three sj)ecimens 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 posterioi-ly, opposite middle of spiracles, 18 mm. 



mm. 



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 flap 61 



Width of mouth 44 



Diameter of iris 11 



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

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



