5. POMACENTKUS. 27 



h. Twenty-six lines long. Cape St. Lucas. Presented by the Smith- 

 sonian Institution. — One of the types of P. hairdii, GiU. 



c. Twenty-four lines long. West coast of Central America. From 

 Captain Dow's Collection. Presented by Dr. P. L. Sclater, Seer. 

 Zool. Soc. 



d-h. Adult, half-grown, and young. Island of Cordova. Presented 

 by J. U. Skinner, Esq. 



After having seen the variations of colours in P. trilineatus, P. leu- 

 costictus, and in many other species of this genus and of Glyphidodon, 

 it is impossible for me to share Professor Gill's opinion as to the 

 validity of three of the four species established by him in the * Pro- 

 ceedings of the Philadelphia Academy,' I. c, P. rectiframum, Jlavi- 

 latus, and bairdii. I am not only indebted to that gentleman for the 

 opportunity of examining typical specimens, but also for an account 

 in MS., in which he distinguishes a fifth form among the numerous 

 examples collected by Mr. Xantus at Cape St. Lucas. I am fully 

 convinced that they are specifically identical, and that the differences 

 pointed out by Professor GiU are dependent chiefly on age, — P. recti- 

 frcenum being the old, and P. bairdii the young state^ AvhUst the 

 other represents a variation of colours similar to that observed in 

 P. leucostictus. However, in order not to omit anything which may 

 assist others to form their own opinion, I insert the following cha- 

 racters assigned by Professor GiU to his species and kindly com- 

 municated to me by him for that purpose : — 



" I. Two blue lines on upper surface of head con- 

 tiauous to occiput. 

 n. Sides, pectoral, caudal, and dorsal and anal fins 



behind, yellowish P. Jlavilatus. 



/3. Sides and fins coloured nearly as back. 



1 . Yentrals and anal not margined ; no dorsal 



ocellus nor anal spot P. rectifrcenum. 



2. Ventrals, and anal in front, margined with 

 blue ; anal with a blue spot at base of last 



rays ; dorsal oceUus P. anaUgutta. 



II. Two blue lines from snout decurved behind eyes. 



1. Body uniformly coloured, with two dorsal 

 spots ; also one behind dorsal fin and one at 

 base of last anal rays ; occiput with a blue 



spot on each side P. quadrigutta. 



2. Body below and tail yellowish, without di- 

 stinct spots ; occiput vnth two parallel lon- 



tudinal blue lines, &c P. bairdii." 



26. Pomacent^us quadrigutta. 

 Gill in Proc. Acad. Nat. Sc. Philad. 1862, p. 149. 



D. ||. A. y^. L. lat. 26. L. tranev. 3 10. 

 The height of the body is contained twice and two -thirds in the 



