12 2 ZOOLOGY OF THE VOYAGE OF THE BEAGLE. 



Colour. — (In spirits.) Greenish-brown, much more uniform than in either of the last two 

 species, not deepening on the back, and scarcely becoming paler underneath. The back 

 sides, and rays of the fins, are finely irrorated with dusky specks, as in the M. alpinus, but not 

 to the same extent, the specks being more thinly scattered, and here and there scarcely 

 visible. From the same cause the fins appear paler. 



Habitat, Bay of Islands, New Zealand. 



This, which is a very distinct species of this new genus, was taken by Mr. 

 Darwin in fresh-water in the Bay of Islands, New Zealand. It is well charac- 

 terized by its more attenuated head and smaller eye, than those of either of the 

 two others. 



Family.— ESOCID2E. 



ExOCCETUS EXSILIENS. HI. ? 



Exocoetus exsiliens, Bl. Ichth. pi. 397. 

 Form. — Head about one-sixth of the entire length, and approaching to the form of a paralle- 

 lopiped ; very much flattened on the crown and between the eyes quite to the end of 

 the snout, broader above than beneath, so that the cheeks are beyond the vertical inclining 

 inwards at bottom. Snout short : mouth not much cleft; when shut, the jaws are equal, and 

 the commissure of the lips appears to extend to beneath the anterior margin of the eye, but 

 the maxillary, which retires completely beneath the suborbital, does not reach so far : when 

 the mouth is open, the maxillary becomes vertical, and the intermaxillary being scarcely at all 

 protractile, the lower jaw is a little the longest. Teeth very minute : a row, scarcely visible, 

 along the forepart of the intermaxillary, but not extending to the sides of the jaw : none that 

 can even be felt in the lower jaw, or in any other part of the mouth. Tongue rounded, and 

 free at the tip. A loose veil of skin hangs down in front of the palate, from immediately 

 behind the teeth in the upper jaw. Eyes round, and very large ; the upper part of the orbit 

 reaching to the line of the profile, and forming a slightly salient ridge : their diameter very 

 nearly one-third the length of the head; between them and the end of the snout is two- 

 thirds of a diameter ; the distance from one to the other across the crown is one diameter and 

 a quarter. The nostrils consist of one large round orifice a little in advance of the eyes. 

 The membrane of the opercle forms a slightly salient angle backwards, near the upper part of 

 the gill-opening. Scales large, of a somewhat irregular form, approaching to oblong, nearly 

 twice as broad as long, the posterior margin with three or four incisions near the middle, and a 

 few rather indistinct nearly parallel striae on the surface of the basal portion ; in others these 

 striae converge to form a small but very regular fan ; and the scales appear to vary a good deal 

 on different parts of the body. 



The pectorals reach exactly to the base of the lateral caudal rays ; the first two rays are 

 simple, and all the others branched ; first ray of all not half the length of the fin. Dorsal so 

 situate as to leave a space between it and the end of the fleshy part of the tail about equal to 

 its own length ; the first ray simple, the others branched ; the last prolonged beyond those 

 which immediately precede it so as to form rather a point backwards. Anal similar to the 



