1. CH^TODOH. 5 



as broad, with the posterior side emarginate. The interoperculum 

 is broader and longer than the suboperciilura. The humerus is rather 

 feeble. The cavity formed by the coracoid and the ulna and radius 

 is broad and deep, and offers a strong basis for the muscles of the 

 pectoral fin, wliich, in these short and elevated fishes, is more strongly 

 developed, in order to maintain the fish in equilibrium, than in those 

 with a more elongate and depressed body. Each pubic bone is formed 

 by three lamellae of nearly equal development, and there is no free 

 space between them. 



There are ten abdominal and fourteen caudal vertebrce, the length 

 of the former portion of the vertebral column being to that of the 

 latter as 1 : 1'4. The ribs are rather strong and broad. The longest 

 neural and hasmal spines are those of the middle vertebrae. The first 

 two haemal spines are the strongest, and excavated anteriorly. Each 

 of the anterior neural and interneural spines is dilated posteriorly in 

 a transparent lamella. The first interhsemal is very strong, and 

 apparently composed of two spines. 



2. Chsetodon plebejus. 

 X. Gm. p. 1269 ; Cut: ^- Val. vii. p. 68. 



D. i|. A.-^. L. lat. 45. L. transv. 6/15. 



The snout is rather obtuse, and nearly equal in length to the dia- 

 meter of the eye ; praeoperculum scarcely denticulated ; the dorsal 

 and anal fins rounded posteriorly. The ocular band reaches from 

 the side of the neck to the inferior margin of the interoperculum, is 

 white- edged, and darker above the eye than below. Tail with a 

 large rounded, blackish, white-edged spot near its back, immediately 

 below the end of the dorsal. 



South Sea. 



a. Adult : rather bleached. Old Collection. 



3. Chsetodon trifascialis. 



Chaetodon trifascialis, Quoy l<f Gaim. Voy. XJran, Zool. ii. p. 379, pi. 62. 

 f. 5 (not good) ; Bleek. Batoe, p. 313. 



bifascialis, Cuv. ^- Vol. vii. p, 48, 



Megaprotodon bifascialis, Guichen. Revue Zool. 1848, p. 12, 



^■T^r ^-dre- L. lat. 28-30, 

 The snout is very slightly produced, somewhat pointed, and shorter 

 than the diameter of the eye ; praeoperculum distinctly serrated ; the 

 dorsal and anal fins with the posterior angle rounded. The ocular 

 band is not wider than the eye, edged with white, and extends from 

 the neck over the chest. Body with oblique blackish streaks, angu- 

 larly bent, with the angle directed forwards ; a broad oblique black 

 band from the soft dorsal to the posterior part of the anal, anteriorly 

 with a broad white margin ; the soft dorsal and anal with a yellowish 



