70 ZOOLOGY OF THE VOYAGE OF THE BEAGLE. 
slightly striated or veined, and not separated from the cheek by any salient ridge. The other 
pieces of the gill-cover taken together are bounded posteriorly by a sinuous and. very irregular 
margin, the notch in the bone at the upper part of the opercle being nearly semicircular, 
beneath which is an obtuse point, whence the obliquely descending margin first slopes slightly 
inwards, then passes outwards to form another blunt point lower down, then slopes inwards 
again. The course taken by the margin of the membrane in some measure follows that of the 
bone, but the sinuosities and salient angles are more rounded. Cheeks and opercle scaly, as 
well as the cranium and forehead between the eyes. 
The lateral line does not deviate very much from rectilineal. The deflection, such as it is, 
may be said to commence in a line with the termination of the first dorsal, and to end beneath 
the first third of the second dorsal. Up to this point, the scales which cover it are small and 
round; but they then begin gradually to enlarge, and to assume a keel terminating posteriorly 
in a short spine: these scaly lamine continue increasing in size till they arrive beneath the last 
quarter of the fin, where they are most developed ; none of them, however, are very large, and 
even here they do not extend over the whole breadth of this part of the tail, nor their own 
breadth exceed one-eighth of the greatest depth of the body. After passing the dorsal and 
anal fins, they rapidly diminish as they approach the caudal. The entire number of lamine 
may be set at thirty-five or thirty-six; but as it is difficult to fix the exact point where they 
commence, it will vary according as the computation is made more or less in advance. ‘The 
anterior portion of the lateral line, bend included, is a little longer than the posterior. 
The reclined spine in this species is entirely concealed beneath the skin. The pectorals 
are long and falcate, terminating in a sharp point: their length nearly equals that of the head, 
or about one-fourth of the entire length: when laid back, they reach over the anal finlet, and 
very nearly to the commencement of the true anal. The ventrals are attached a little behind 
the pectorals, and are only half as long. The other fins are much as in the other species of 
this genus. The height of the anterior part of the first dorsal equals exactly half the depth. 
The lobes of the caudal are one-fifth of the entire length. 
Cotour.—Not noticed in the recent state. Jn spirits; silvery on the abdomen and lower half of 
the sides, passing above the middle, and on the back, into pale lead blue, tinged with gray and 
brownish: fins pale greyish brown. No conspicuous markings, except the usual spot on the 
notch of the opercle, which, however, is small, and confined entirely to the membrane. 
Habitat, Tahiti. 
This species belongs to the second section adopted by Cuvier and Valen- 
ciennes in this genus; or that in which the form of the body resembles that of the 
C. trachurus, but in which the lamine on the lateral line only extend over the pos- 
terior portion, the anterior being smooth and simply covered with small scales. But 
it will not exactly accord with any of the species described by those authors. It 
seems to approach most nearly the C. Plumieri; but though the eyes are of 
considerable size, they are not quite so large as they are represented to be in that. 
There seem, in fact, to be several species characterized by large eyes. Spix and 
Agassiz have figured one from America under the name of C. macrophthalmus ; 
and under the same name Ruppell has figured another from the Red Sea. Both 
