FISH. 129 



intervals ; then follow a row of close, minute, sharp teeth, similar to those on the edge of the 

 maxillary. Eyes rather large, their diameter not quite one-fourth the length of the head, dis- 

 tant one diameter and a quarter from the end of the snout. Suborbital large, consisting of 

 three pieces. Preopercle rectangular. A row of pores, not very distinct, along the under 

 part of the lower jaw, thence continued along the limb of the preopercle. Opercle and sub- 

 opercle taken together with the posterior margin forming a slight but regular curve, with 

 scarcely any salient angle. 



Head naked ; scales on the body of moderate size, arranged in somewhat oblique rows, 

 especially below the lateral line ; one from the middle of the side below the lateral line of an 

 irregularly rounded form, the posterior margin rather sinuous, the disk with numerous fine 

 concentric striae, but no deeper- cut striae on the basal portion. About sixteen scales in a ver- 

 tical row, and fifty-seven or fifty-eight in the lateral line : this last bending downwards in a 

 curve which falls below the middle of the depth. Scales on the lateral line not larger than the 

 others. 



The dorsal answers to the space between the ventrals and anal ; its height equals the depth 

 to the lateral line. Anal long, commencing exactly under the last ray of the dorsal ; the first 

 part of this fin as high as the dorsal, but the rays, beyond the fifth, gradually decreasing ; three 

 spines, the first two very minute ; the last soft ray double. Caudal in this specimen injured. 

 Adipose and last ray of the anal in the same vertical line. Pectorals two-thirds the length of 

 the head, attached very low down beneath the terminating portion of the gill-flap, narrow and 

 slightly falcate, reaching to the ventrals, which last are one-fourth shorter. A long narrow 

 scale in the axilla of each ventral one-third the length of the fin itself. 



B. 4; D. 11 ; A. 3/26; C. 22, &c. ; P. 12; V. 8. 



Length 4 inches 3 lines. 



Colour. — " Bluish silvery." — D. — Some appearance of a dusky spot at the base of the caudal pro- 

 longed in a line along the middle rays, but scarcely any trace of a humeral one. The dorsal 

 and anal incline a little to dusky. 



Taken at Maldonado, in a fresh-water lake, in June. I have scarcely any 

 doubt of its being the H.falcatus of the Zoology of Freycinet's voyage, the figure 

 of which it exactly resembles, excepting that the humeral dark spot, if it ever 

 existed, and which is not mentioned in Mr. Darwin's notes, is now almost entirely 

 effaced. It is probable, however, that there are two or three species nearly allied, 

 for which reason I have been the more particular in my description. The H. 

 Ilepsetus of D'Orbigny* appears to differ from the H. falcatus of Freycinet (with 

 which lastCuvier associates his name of Hepsetus,) in having the lateral line curv- 

 ing upwards rather than downwards, and the caudal fascia as well as the humeral 

 spot more marked. The Sabno falcatus of Bloch is probably distinct from both 



* Voi/. dans L'Amer. Merid. Atl. Ichth. pi. 9. fig. 2. 



S 



