1. CHJiTODON. 5 



as broad, with the posterior side emarginate. The interoperculum 

 is broader and longer than the subopercuhim. The humenis is rather 

 feeble. The ca%-ity 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, which, 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 dejjressed body. Each pubic bone is formed 

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

 space between them. 



There are ten abdominal and fom-teeu caudal vertehrce, 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 

 neui-al and haimal spines are those of the middle vertebrae. The fii'st 

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

 of the anterior neural and interneural sijines is dilated posteriorly in 

 a transparent lamella. The first interhtemal is veiy strong, and 

 apparently composed of two spines. 



2. Chaetodon plebejus. 



L. Gm. p. 1269 ; Cur. Sr Veil. 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 ; pra3operculum 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. Chaetodon trifascialis. 



Chfetodon trifascialis, Quoi/ ^ Gaim. Vuy. TJran. Zool. ii. p. 379. pi. 62. 

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



bifascialis, Ctiv. %■ Val. vii. p. 48. 



Megaprotodon bifaseialis, Gulchen. Revue Zool. 1848, p. 12. 



D-T^,- A.^. L. lat. 28-30. 



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

 than the diameter of the eye ; prseoperculum 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 dii'ected forwards ; a broad oblique black 

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

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



