NATURAL SCIENCES OF PHILADELPHIA. 217 



Behind the end of the supramaxillary, there is a vertical blue bar. The scales 

 of the cheeks and opercula are spotted with blue in the centre. Lips immacu- 

 late brown. The dorsal fin on its scaly portion is similar to the back ; the 

 anal has a blue spot at the base of its last rays, and its front, like the outer 

 edge of the ventral fin, is blue. The pectoral inside has also a blue line across 

 the base of the upper rays. 



As the fish advances in age, the blue on the centres of the scales fades, and. 

 finally, the color of the whole body, as well as the scaly portions of the fins, 

 become a purplish-brown ; but the spots on the scales above the first, seventh 

 and fifteenth (sixteenth) scales of the lateral line remain, as does also the one 

 bordered before by blue in the rear of the dorsal fin. The coloration on the 

 head simply becomes fainter, and the lines narrower and somewhat inter- 

 rupted. The fins are uniform and spotless, except the pectoral, which retains 

 the transverse bar which was assumed in its youth. 



This species, in its young state, was formerly described as a Pomacentrus, 

 the preoperculum having a scolloped appearance, produced by the muciferous 

 ducts and their mouths, and thus simulating the serrature of young Pomaeen- 

 tri, misleading Dr. Giinther as well as myself, especially as it had the color- 

 ation and form of a Pomacentrus. The border in the old is not so much ex- 

 posed, and is perfectly entire, while the preorbital has gained in elevation at 

 the expense of the eye. The uniform color of the body is also in strong con- 

 trast to the variegated sides and fins of the young. 



The smallest specimen obtained by Mr. Xantus is nearly an inch and a half 

 long ; and nine were obtained varying from that length to little more than 

 two inches, none offering any essential difference. A single adult, distorted. 

 and presenting a peculiar appearance, having a length of little more than four 

 inches, was also collected. 



POMATAPRION BAIRDII Gill. 



Pomacentrus Bairdii Gill, Proc. Academy of Natural Sciences of Phila., 1862, 



p. 149. Gill in Giiniher's Catalogue of the Fishes, &c, vol. iv. p. 27. 

 Pomacentrus rectifrsenum pt. Giinther, (excl. desc.) 



The color in extreme youth, as represented by a specimen ten lines long, is 

 greenish-yellow, modified by blue above on the middle of each scale, the 

 margins alone being brownish ; below a line drawn from the axil of the pec- 

 toral to that of the dorsal fin, the blue has disappeared, and the brownish- 

 yellow is conspicuous, sprinkled over with a few faint, darker dots, which 

 themselves become obsolete on the abdomen and caudal peduncle ; immedi- 

 ately behind the dorsal fin there is a dark spot, margined in front by blue. 

 The head above has two blue lines continued from snout and decurved over 

 the eye-ball and behind the orbit ; on the forehead there is a transverse blue 

 bar, and on the nape two nearly parallel longitudinal blue lines. An oblique 

 blue bar crosses the preorbital ; a series of blue dots on the suborbital chain 

 is continued to meet the deflected line behind the eye, and there is a blue bar 

 behind the end of the maxillary. The lips and opercula are brown. The 

 dorsal fin, on its scaly portion, including all the spinous portion, except a 

 marginal band, and the lower half of the soft, is blue, the scales scarcely 

 being margined by brown ; the other fins are colorless, except the margin of 

 the anal, which is dark. 



The species, with advancing age, loses the intensity of the blue above, but 

 that color spreads downwards faintly, and is perceptible on all the scales ex- 

 cept those of the abdomen and hinder portions of the caudal peduncle. The 

 blue on the upper surface of the head and the preorbital finally becomes ob- 

 literated, but the series on the infraorbital chain and the bar behind the 

 maxillary remains, while the opercula assume blue dots. The fins also, es- 

 pecially the ventral and anal, have become dusky. 

 I have seen nine specimens of the Pomataprion Bairdii, from Cape St. Lucas 



1863.] 16 



