78 ZOOLOGY OF THE VOYAGE OF THE BEAGLE. 
specimen. Mr. Darwin took it at Maldonado, where he states that it is very 
common, adding that it is sometimes found in brackish water. M. D’Orbigny 
had also found it previously at the mouth of the Rio Plata. 
2. ATHERINA MICROLEPIDOTA. Jen. 
Prate XVI. Fig. 1. Nat. size. 
Fig. 2. a, 6. Magnified scales. 
A. gracilis ; corporis altitudine partem octavam, capite quintam, longitudinis 
e@quante: oculis mediocribus : mawillis sub-equalibus, parum protractilibus ; com- 
missurd primum horizontali, deinde paulo deflexd, haud oculos attingente: dentibus 
velutinis, serie externa supra subtusque fortiori: dorsali prima omnino pone ventrales 
reclinatas locata: squamis parvis, seriebus longitudinalibus octodecim ad minimum 
dispositis. 
Di a—Wtle Avtity= Cy lake. Pts. Vo Lio. 
Lone. une. 4. 
Form—More slender and elongated than the generality of the species in this genus. Greatest 
depth not more than one-eighth of the entire length. Head one-fifth of the same. Greatest 
thickness (in the region of the gills) equalling two-thirds of the depth, or rather more. 
Ventral line of the body scarcely more curved than the dorsal. The upper profile falls, though 
very slightly, from the nape to the mouth, and the lower profile inclines upwards to meet it at 
about the same degree of curvature. Head broad, its breadth across the crown nearly 
equalling its depth. Snout horizontally rounded. Jaws nearly equal; not so protractile as in 
some other species: the commissure of the lips at first horizontal, but posteriorly inclining a 
little downward, and scarcely reaching more than half-way to the eye. In each jaw two rows 
of slender very distinct teeth, with traces of a third or even fourth row above, towards the 
middle : outer row longest and most conspicuous, consisting, in the upper jaw, of from forty- 
five to fifty teeth; in the lower of scarcely more than twenty-five. No teeth that can be 
seen on the vomer or palatines, though a slight roughness can be felt on both. Eyes of 
moderate size; their diameter rather more than one-fourth the length of the head; almost 
entirely before the middle, as well as above it: space between the eyes flat, and exceeding the 
diameter by about one-third : a slightly elevated line on each side of this space, but no other 
conspicuous sculpture. Opercle with the descending margin sloping obliquely forwards. 
Crown, cheeks, and gill-covers scaly, the scales on the crown extending as far as the 
eyes. Scales on the body small, the number of longitudinal rows amounting to eighteen or 
twenty : in form nearly square, the length a little exceeding the breadth, the superficies marked 
with numerous very distinct concentric lines, the basal half with a fan of from four to six 
deeper cut striz, the basal margin rather sinuous, and obsoletely crenate where the strize meet 
it. No lateral line very distinguishable. 
First dorsal small and delicate, commencing exactly at the middle point of the entire 
length, measuring this last to the bottom of the caudal fork, and in a line with the tips of the 
ventrals, these last fins being laid back. Space between the first and second dorsals a little 
exceeding two-thirds of the depth of the body. Length and height of the second dorsal equal 
