THE SHORE FISHES OF PERU 65 



large serrated spine, bearing fin folds posterior to spine, forming a 

 narrow caudal fin; upper surface with or without spines and prickles, 

 most frequently with spines on median line of back and taU. 



The species of this genus are not well known. As there probably 

 is considerable variation especially in the development of spines and 

 spinules with age and sex, much larger series of specimens than now 

 available are needed to determine which differences actually are of 

 specific value. While making this study specimens of all the species, 

 exclusive of two, recognized from the Pacific coast of America have 

 been at hand for comparison. 



KEY TO THE SPECIES 



a. Caudal fin rather wider than eye, broadly rounded; disk smooth, entirely 

 without spines or prickles; tail without lateral spinules; teeth without 



cusps serrula, new species (p. 65) 



aa. Caudal fin narrower, not wider than eye, narrowly rounded; disk with few 

 prickles on snout and a strong nuchal spine; tail with a series of lateral 

 spinules and a series of low tubercles on dorsal fin fold; teeth without 



cusps caudispinosus, new species (p. 67) 



aaa. Caudal fin vc^ry narrow, sharply pointed; prickles on snout, with or without 

 spines on back; tail without lateral spines; teeth with small cusps. 



peruanus, new species (p. 69) 



UROTRYGON SERRULA, new species 



Figure 13 



Disk broader than long, rather pointed anteriorly, its anterolateral 

 margins nearly straight and oblique to opposite front of eyes, convex 

 elsewhere, broadest opposite about the third pair of gill slits; its 

 width 1.8 in total length; its greatest length 1.95; length anterior to 

 axil of pectoral 2.2; length anterior to vent 2.3; length posterior to 

 vent 1.9 ; tail from axil of ventral to its tip slightly shorter than greatest 

 length of disk, depressed at base, its depth at axil of ventral 1.65 in 

 its width at same place, becoming compressed distally, with a rather 

 broad dermal fold above and below, forming a rather wide, broadly 

 rounded caudal fin, somewhat broader than eye in widest place; 

 caudal spine slender, very sharply pointed, a little longer than the 

 snout, posterior half with sharply serrate margins, except on the 

 spearlike tip; snout little exserted, rather pointed, its length anterior 

 to eye 3.45 in length anterior to axil of pectoral, its preoral length 3.8; 

 interorbital 8.6; internarial space 8.6; eye and spiracle about equal, 

 4.15 in snout; mouth transverse, its width 8.0 in length anterior to 

 axil of pectoral; teeth with low ridges, but no cusps; disk smooth, 

 entirely without prickles or spines; tail smooth; ventral very broadly 

 rounded distally, the outer (lateral) part not especially produced, 4.8 

 in length anterior to axil of pectoral; claspers in the probably young 

 male at hand scarcely as long as the fin next to it, and shorter than 

 outer margin of ventral. 



