NATURAL SCIENCES OF PHILADELPHIA. 



215 



POMACENTRUS RECTIFRjENUM Gill. 



Pouiacentrus rectifrsenum Gill, Proc. Academy of Natural Sciences of Phila., 



1862, p. 148. 

 Pomacentrus rectifrsenum Giinther, Catalogue of the Fishes in the British 



Museum, vol. iv. p. 26. 

 Pomacentrus rectifrasnum Gill, in Giinther's op. cit., vol iv. p. 27. 

 Pomacentrus analigutta Gill, in Giinther's dp. cit., vol. iv. p. 27. 



This species undergoes great change with age, and on two suites of speci- 

 mens two nominal species were formerly based, the author having been de- 

 ceived by the comparatively long retention of the colors of the young in 

 several individuals, and the early assumption of the adult state by others. 



The color in extreme youth, as represented in a specimen eight Hues long, 

 is reddish-brown, with blue lines obliquely crossing each scale, and forming 

 as many subvertical, scarcely interrupted blue lines crossing the body as 

 there arc rows of scales. On the back and lower part of the anterior soft dorsal 

 is a large ocellus, and behind the fin is a smaller one. The head above has two 

 very distinct blue lines continued from the snout over each eye, where they. 

 are most distant, and again approximating and continued, one on each side 

 of the base of the dorsal fin, but under the fin rather broken into a linear row 

 of spots ; another line crosses the eye-ball above, and behind the upper angle 

 of the orbit is a line which is continued to the row of scales above the lateral 

 line ; a bar crosses the preorbital ; a line runs along the suborbital chain ; 

 another line extends backwards from the corner of the mouth, and under the 

 suborbital one ; and a blue line colors the upper lip. Ou each of the opercu- 

 lar scales is a bluish blotch. The dorsal and anal fins are spotted with blue, 

 a spot existing on each scale, and a blue bar crosses the base of the last 

 anal rays. The caudal is brownish, as are also the pectorals. The ventrals 

 dark, and the spine outside bluish, like the front of the anal. 



These colors are retained until the fish has attained a length of more than 

 two inches, the chief change being effected by the slightly greater isolation of 

 the spots on the rows above the lateral line, so as to break their continuity as 

 lines ; and especially in the fading away of the blue ring and ocellus of the 

 dorsal, which has then become very faint, and is the first to disappear. Fi- 

 nally, in the very aged specimens, more than three inches long, the color of 

 the body and scaly portion of the fins has become almost a uniform brownish- 

 chesnut ; and very indistinct traces of the lines on the upper surface and 

 sides of the head are perceptible. The naked portions of the dorsal and anal, 

 as well as the ventral fins, are very dark, and the pectorals yellowish, 

 The profile is also apparently steeper and more convex ; and the body more 

 obese. 



In studying the development of this species, I have had before me not less 

 than thirty-two individuals, exhibiting every gradation, from the specimen eight 

 lines long to one nearly three inches and a half long, having discovered 

 since my former studies several important specimens in a collection made at 

 Panama by Oapt. Dow. My opportunities for knowing the changes of this 

 species, as well as the West Indian ones, have, therefore, been much greater 

 than Dr. Giinther's. 



Pomacentrus flavilatus Gill. 

 Pomacentrus flavilatus GUI, Proc. Academy of Natural Sciences of Phila., 



1862, p. 148. Gill, in Giinther's Catalogue of the Fishes in the British 



Museum, vol. iv. p. 27. 

 Pomacentrus rectifrasnum pt Giinther, (excl. desc.) 



This species, so far as known, undergoes little change during its progress 

 to adult age. 



The color above the lateral line, and on the scaly portion of the dorsal fin 

 before the middle of its soft part, is dark-brown, with blue on the centre of 



1863.] 



