!54 PAPERS FROM TORTUGAS LABORATORY vol. xxxiv 



Holacanthus isabelita (Jordan and Rutter) 



No discussion was found among Dr. Longley's manuscripts, and it is very 

 difficult to decide which of his notes apply to this species. For a long time Dr. 

 Longley was unable to determine definitely to which species to assign the fishes 

 observed. He expected four species of Holacanthus until 1922, when he seems to 

 have concluded that Angelichthys toicnsendi Nichols and Mowbray (Bull. Amer. 

 Mus. Nat. Hist., vol. 33, 1914, p. 581) probably was a cross between H. ciliaris 

 and H. isabelita. Furthermore, he seems to have concluded that the fish he had 

 tentatively identified as townsendi actually were ciliaris, of which he had seen 

 only ^ individuals. All notes, other than the few referring to the 3 fish finally 

 identified as ciliaris, and those concerning tricolor (a species which never was in 

 doubt), must then apply to isabelita or townsendi (the latter a hybrid). I find it 

 impossible, however, to untangle the two. 



It can only be stated here that this species seems to be fairly common on the 

 reefs at Tortugas. 



I find the following significant note among Dr. Longley 's papers: "Angelich- 

 thys isabelita has no ocellus at nape. Border only of caudal is yellow. These two 

 characters are enough to identify it." 



The young seem to have two or three pale blue vertical bars on the posterior 

 part of the body, in addition to a "vertical dark bar through eye, meeting its 

 fellow on occiput and at throat. Throat and breast to base of pectorals washed 

 with blue. Posterior margins of preopercle and opercle blue, giving two vertical 

 stripes." No notes on the color of the adult were found. The crossbars, however, 

 seem to disappear with age. 



Concerning townsendi, recognized as a hybrid, I find the following note, 

 apparently based on a verbal statement by Louis L. Mowbray : "The caudal is all 

 yellow. There is a blue blotch on the nape, but not the well defined ocellus of 

 ciliaris. The sides and dorsal fin are more bluish than in isabelita!' 



West Indies to Florida. S. F. H. 



Family ACANTHURIDAE. Surgeonfishes 

 Acanthurus Forskal, 1775 



Key to the Species 



a. Body deep, ovate, depth about 1.5; anterior profile very steep, straight 

 to slightly concave over snout; D. IX,27; A. 111,25 or 26; caudal 



lancelet always pale caeruleus 



aa. Body more elongate, depth about 1.75 to 2.0; anterior profile less 

 steep, more or less convex; D. lX,2^ l / 2 or 25%; A. III^oH to 24 x /i\ 

 caudal lancelet dark 

 b. Caudal fin lunate, upper lobe not much longer than lower one; 

 sides with a series of narrow vertical dark lines (sometimes 

 missing in preserved material); caudal fin without pale margin . hepatus 

 bb. Caudal fin deeply lunate, upper lobe notably longer than lower 

 one; no vertical bars on sides; caudal fin with a white margin 

 posteriorly bahianus 



S. F. H. 



