THE SHORE FISHES OF PERU 



353 



by two short dark bands on lower part of head, generally not meeting 

 ventrally, the last one scarcely more than a blotch in some specimens; 

 pectoral with a narrow dark band at base, the fin otherwise plain 

 olivaceous; the other fins dusky gray, variously marked with pale 

 and dark specks; margins of caudal and anal pale. 



This species is represented in the collection made by the Mission 

 by eight specimens, 40 to 85 mm. (30 to 68 mm. to base of caudal) 

 long, all taken in shallow water in Lobos de Afuera Bay. The 

 largest specimen (U.S.N.M. No. 128113) has been selected as the 

 type. The following proportions and enumerations are based on the 

 type: Head 3.25 in length; depth 3.0; ventral 5.6; pectoral 4.5. 

 Eye in head 4.3; snout 3.0; interorbital 3.1; maxillary 4.2; caudal 

 peduncle 1.9; ventral 1.75; pectoral 1.4. D. IX, 10; A. Ill, 9; P. 14; 

 scales in lateral series 25, one complete and a partial row between lat- 

 eral line and first dorsal spine, six scales in upper row on cheek, five 

 in lower row, eight along margin of opercle below angle (including 

 scale at angle), four before dorsal, and five before ventral. 



The Peruvian examples seem to be closely related to S. azureus 

 Meek and Hildebrand (1928, p. 742, pi. 72, fig. 1), which is known 

 only from the type (U.S.N.M. No. 81778) from Panama Bay. Upon 

 comparison of specimens, several differences were noticed. Some, 

 but not all, of the differences may be ascribed to a difference in age 

 or size, as the Panama fish, having a length of 200 mm., is much 

 larger. The name duhius is offered because the meager material 

 available leaves the exact relationship of the two species in doubt. 

 The following comparison shows the differences noticed: 



S. azureus S. duhius 



Pectoral rather narrow, the rays de- 

 creasing rapidly in length, the lower- 

 most one about a third the length of 

 the longest one, with 15 rays. 



Ventral fin long, 1.6 in head, 5.2 in 

 length; first (outermost) divided ray 

 a little longer than the second; last 

 ray about half the length of first. 



Scales on median line before dorsal 5. 



Scales on cheek in 3 rows, the 2 upper- 

 most rows each with 6 scales, the 

 third with 1 scale. 



Scales along margin of opercle below 

 posterior angle 10 (including large 

 scale at angle). 



Gill membranes separate. 



Pectoral broad, the rays decreasing 

 more gradually in length, the lower- 

 most one half the length of the longest 

 one, with 14 rays. 



Ventral fin shorter, 1.75 to 2.2 in head, 

 5.9 to 6.6 in length; second divided 

 ray a little longer than the first 

 (outermost) one; last ray about three- 

 fourths of first. 



Scales on median line before dorsal 3 in 

 1 specimen, 4 in 6, and 5 in 1. 



Scales on cheek in 2 rows, uppermost 

 row with 5 scales in 7 specimens, with 

 6 scales in 1 example. 



Scales along margin of opercle below 

 posterior angle 8 in 6 specimens, 7 in 2 

 examples (including large scale at 

 angle) . 



Gill membranes narrowly united across 

 isthmus. 



