THE SHORE FISHES OF PERU 73 



found that the fish from the two locaUties differ in several respects. 

 Some of the differences may be attributable to the differences in age 

 and size, though it seems higlily improbable that all of them can be 

 accounted for in that way. 



The disk in the Peruvian fish differs both in shape and proportions. 

 It is more pointed anteriorly, the snout forming an angle of about 

 110°, and its margins opposite snout, eyes, and spiracles are straight. 

 In the Mexican fish the snout forms an angle of about 125°, and its 

 margins opposite the snout, eyes, and spiracles are definitely convex. 

 The differences in proportions are shown in table 1. 



The eye in the Peruvian fish is much smaller than the spiracle, the 

 longest diameter of eyeball being only about three-fourths the longest 

 diameter of the spiracle. In the Mexican skates the eye and spiracle 

 are about equal in size. Some differences in proportions of the eye, 

 interorbital space, interspiracular space, and snout are shown in 

 table 1. 



The teeth in the Peruvian specimen are not definitely in pavement 

 but are in a band, each tooth having a very small base, which is 

 transversely scarcely elongate, and each has a prominent cusp. In 

 the larger Mexican specimen, also a male, the teeth definitely are flat 

 and in pavement, each tooth having a broad, transversely elongate 

 base and a very small cusp posteriorly. 



The claspers in the Peruvian specimen, though the fish is much 

 larger than the larger Mexican specimen, are proportionately shorter. 

 In the former the part of the clasper free from the ventral is notably 

 shorter than the fin, w^hereas in the latter the free part is about equal 

 to the length of the ventral. Some proportions are shown in table 1. 



Whether the specimens reported as P. crehri])unctata from Panama 

 by Gilbert and Starks (1904, p. 18) belong to either species compared 

 in the preceding paragraphs cannot now be verified from specimens, 

 as no Panama material is at hand. Insufficient specimens obviously 

 are available to determine variations. It is possible, though improb- 

 able, when more specimens become available for study, that all the 

 Pacific coast specimens from the Americas may be found to be of one 

 species. It seems advisable at present to consider the Peruvian skate 

 as specifically distinct from the Mexican one. 



The Peruvian skate also was compared with two males, 330 and 

 335 mm. wide (U.S.N.M. No. 94545), from Corpus Cliristi, Tex., 

 identified as P. micrura. In general, the differences in the shape of 

 the disk are the same as in the Peruvian and Mexican skates, and the 

 differences in the teeth also are the same. The claspers in Texas 

 specimens agree essentially in size and proportions with those of 

 Peruvian fish, these organs in examples of about the same size being 

 decidedly smaller than in the JMexican fish. The Texas fish differ 

 from both Pacific coast species in having a slight fold on the median 



