THE SHORE FISHES OF PERU 427 



compressed, its depth 2.7, 3.3 in head; head convex above; snout 

 moderate, 6.7, 7.1 in head; eye 3.8, 3.9; interorbital 4.0, 4.2; mouth 

 obHque, the lower jaw included; maxillaiy reaching under anterior 

 margin of eye, 4.0, 4.7 in head; teeth in a single, irregular, labial 

 series in each jaw, those of the lower jaw exceedingly small; preorbital 

 strongly serrate; opercle entirely scaleless; cheek with two rows of 

 scales; scales on body mostly missing, those present (along back) 

 with smooth edges and strong concentric rings; first dorsal origin a 

 little nearer tip of snout than base of caudal; second dorsal origin a 

 little behind that of anal and a little nearer origin of first dorsal than 

 base of caudal; anal a little longer than second dorsal, its base 7.5, 

 7.75 in length; ventral inserted in advance of tip of pectoral, a little 

 nearer tip of snout than middle of anal base; pectoral short, somewhat 

 rounded, 2.15 in head in one specimen, damaged in the other. 



Color very dark above, silvery elsewhere; gill covers brilliantly 

 silvery, not translucent; base of caudal with a dark bar; snout and 

 margins of lower jaw black; ventral and anal pale; other fins more or 

 less dusky. 



The foregoing description is based on two specimens, 37 and 39 mm. 

 (30 and 31 mm. to base of caudal) long, from Mazorka Island, in the 

 Huaura Group, the only ones obtained by the Mission. This species, 

 although long known from Chile and from Ecuador, has previously 

 not been recorded from Peru under this name. It is believed, how- 

 ever, as explained above, that M. ciliilabis Cuvier and Valenciennes 

 is this species. The identification with M. curema of the two small 

 specimens secured by the Mission is a bit uncertain because each 

 specimen has only 9 soft rays in addition to 2 spines, in the anal fin, 

 whereas the almost constant number for this species for the young is 

 2 spines and 10 soft rays, and for adults 3 spines and 9 soft rays. 

 However, variations have been reported. Among 3 specimens from 

 the Pearl Islands, Panama, now at hand, 1 specimen has 2 spines and 

 only 9 soft rays, whereas the others have the usual number of rays. 



In the young up to a length of about 85 mm. the opercles remain 

 naked and very bright silvery, as shown by specimens from Panama 

 and elsewhere. Thereafter they become covered with scales and lose 

 some of the bright silvery sheen. The first soft ray of the anal is 

 transformed into a spine at a length of about 60 mm., there being 

 some variation among specimens. Wlien the fish have attained a 

 length of about 50 mm., the scales on the chest develop spines along 

 the margins, which extend back somewhat on the surface of the scale, 

 making the scales rough to the touch. According to a limited num- 

 ber of specimens examined, this ctenoidlike condition of the scales 

 spreads to the sides of the fish in young adults, though the spines 

 become smaller again in large specimens. Scales are present on the 

 bases of all the fins, exclusive of the spinous dorsal, even in the smallest 

 specimens (35 to 40 mm. long) at hand, which include the Peruvian 



