60 ZOOLOGY OF THE VOYAGE OF THE BEAGLE. 



to form a point backwards. Caudal forked nearly to its base ; the lobes much elongated ; the 

 upper one, which is a trifle longer than the lower, contained rather more than three times and a 

 half in the entire length. Pectorals narrow and pointed, a little shorter than the head, and 

 contained not quite four times and a half in the entire length ; fifth and sixth rays longest. 

 Ventrals attached a little behind the pectorals, and not much more than half their length ; the 

 spine about three-fourths the length of the soft rays, and scarcely stouter than the third spine 

 in the anal : the axillary elongated scale three-fourths the length of the spine. The scales on 

 the body of this species are not materially different from those of the G. Plumieri described in 

 the " Histoire des Poissons." 



B. 6; D. 9/10; A. 3/7; C. 17, &c. ; P. 16; V. 1/5. 



Length 7 inches. 



Colour. — "White, silvery." — D. The fins are yellowish ; the membranes here and there dotted 

 with black : the lobes of the caudal are bordered internally with dusky. I see no trace of the 

 interrupted longitudinal bands spoken of by Cuvier and Valenciennes, neither is there any 

 allusion to them in Mr. Darwin's notes taken from the recent fish. 



Habitat, Keeling Island, Indian Ocean. 



I do not feel confident as to this species being, any more than the last, 

 identical with that to which I have referred it. It requires an inspection of a 

 large number of specimens in order to ascertain the true value of characters. 

 The present one agrees with what is stated of the G. Oyena by Cuvier and 

 Valenciennes, excepting that the second anal spine, which they represent as 

 shorter than the second dorsal spine by one-half, is here shorter by one-third only : 

 also, as mentioned above, there is no appearance of any longitudinal bands. 

 There is no other species in the " Histoire des Poissons," to which it approaches 

 more closely. But comparing it with Ruppell's figure, if this last be scrupulously 

 exact, there are a few other differences besides those already alluded to. Thus 

 the first anal spine in Mr. Darwin's specimen appears shorter in relation to the 

 second, and this last stouter as well as longer. Also the soft rays of this fin 

 gradually decrease, giving a sloping direction to the margin, whereas in Ruppell's 

 figure, all the rays are nearly of the same length, and made equal to the second 

 and third spines. The caudal lobes, likewise, appear longer in Mr. Darwin's 

 specimen. It must be left for others to determine whether these discrepancies 

 are indicative of a specific difference or not. As regards the geographic range of 

 the G. Oyena, I know not that there is any thing in this respect to render its 

 identity with the species here described improbable. It inhabits the Red Sea ; 

 and is also said to be common at the Mauritius ; — whence it may very possibly 



