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 lamina; 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 laminae 

 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 heigrht 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. 

 Colour. — Not noticed in the recent state. Inspirits; 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 laminae 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 



