FISH. 13 



body are moderately large. There are rows of small scales between the rays of the vertical fins, 

 but they are more developed between the soft rays than between the spinous. The dorsal has 

 the first spine half the length of the second, which itself is a little shorter than the third ; 

 fourth, fifth, and sixth equal and longest ; there is very little difference in the lengths of the 

 remaining rays, nor is there much between the spinous and soft portions of the fin, which, taken 

 as a whole, appears nearly even throughout. Anal short, commencing in a line with the fourth 

 soft ray of the dorsal, and terminating at the same distance from the caudal as that fin : second 

 and third spines very stout. Pectorals narrow and pointed, a little shorter than the head. 

 Ventrals a little shorter than the pectorals. 



B. 7 ; D. 10/14, the last double; A. 3/8, the last double; C. 17, and some short 



ones; P. 16 ; V. J/5. 



Length 6 inches. 



Colour. — " Upper part pale lead colour : pectorals yellow ; ventrals and anal orange: sides very 

 pale yellow." — D. In spirits, the colour appears almost uniform greyish-white. The dorsal 

 and anal fins have an edging of black, which is not noticed by Mr. Darwin, and which is 

 characteristic of the species. The caudal is entirely dusky. There are no traces of spots on 

 any part of the body. 



Habitat, Keeling Island, Indian Ocean. 



All the known species of Diacope are stated by Cuvier and Valenciennes, as 

 coming from the Indian seas. The D. marginata was first brought from thence 

 by Commerson. It was afterwards received by the authors above mentioned 

 from Pondicherry. The expedition under Captain Duperrey, met with it at the 

 Island of Oualan. Mr. Darwin's specimen was obtained at the Keeling or Cocos 

 Islands : I believe it to be referrible to this species, as it possesses the charac- 

 teristic black edging on the dorsal and anal fins ; but as the description in the 

 "Histoire des Poissons" is very brief, containing a mere notice of the colours, I 

 have thought it advisable to annex that of the present individual. 



Genus— ARRIPIS. Jen. 



Membrana branchialis septem-radiata ; apertura ampld. Pinna dor salts unica; spirits 

 gracilibus. Dentes aculeiformes, tenues ; serie maxillari externa cceteris fortiori. 

 Operculum mucronibus duobus parvis postice armatum. Preoperculum marginibus 

 basali et adscendenti denticulatis ; spinis nullis. Ossa infraorbilalia leviter denti- 

 culata. Os maxillare squamosum. Squamce corporis levissime ciliatis, postice 

 striis levissimis, transversis, parallelis, flabelli locum occupantibus. 



I propose to establish this new genus for the reception of the Centropristes 

 Georgianus of Valenciennes, which appears to offer sufficient peculiarities to 



