FISH. 105 
crenatures. Lateral line interrupted; its first portion at the depth of two and a half rows of 
scales beneath the dorsal, and stopping beneath the commencement of the soft part of that fin ; 
recommencing three rows lower down, exactly in the middle of the depth, whence it runs 
straight to the caudal. 
Dorsal commencing above the opercle; the spinous portion of nearly uniform height, and 
scarcely more than one-fifth of the depth; the soft portion much higher, and terminating in a 
sharp point behind. Anal answering to the posterior half of the dorsal, terminating opposite to 
it, and similarly pointed; with six spines, which, as well as the dorsal spines, are furnished 
with very conspicuous filamentous tags. Caudal nearly even. Pectorals rounded, but not 
very broad, their length rather more than three-fourths that of the head; the rays rather slen- 
der. Ventrals pointed; the first soft ray elongated, and reaching to the anal when laid back ; 
the last ray attached at its base by a membrane to the abdomen. ows of small scales between 
the rays of the caudal at the base of the fin; and a few small ones along the base of the dorsal 
and anal, more particularly on the soft portions. 
Cotour.—“ Above, greenish black ; the sides paler ; slightly iridescent..—D.—In spirits it appears 
of a nearly uniform brown all over, fins included. 
Habitat, Maldonado, Rio Plata. 
Mr. Darwin obtained this species at Maldonado, in a lake of fresh water, said 
sometimes to be a little brackish. It appears to belong to the genus Chromis of 
Cuvier, placed by him amongst the Ladbride, but having evidently very strong 
affinities to some of the Scienide. It differs essentially from the C. Brasiliensis 
of Quoy and Gaimard,* in having six anal spines, and being destitute of all 
markings and spots. I am not aware that it is described by any author. 
1. ScARUS CHLORODON. Jen. 
Prate XXI. 
S. @ruginoso cyaneus, capite et pinnis flavo-vittatis: mawillis exteriis levibus, mar- 
ginibus crenatis; caninis ad angulos oris nullis: fronte gradatim proclivi: lined 
lateralt tubis parum ramosis : squamis ubique striato-granulatis : pectoralibus acu- 
minatis, radiis supertoribus arcuatis:; caudali radiis externis ceteris longioribus, 
acuminatis. 
D. 9/10; A. 3/9; C. 13. &e.; P.15vel16; V. 1/5. 
Lone. unc. 16. 
Form.—Of an oval form; the greatest depth one-third of the length, caudal excluded: dorsal and 
ventral lines equally convex. Head a little less than the depth of the body, not gibbous in 
front, but with the profile falling regularly and gradually from the commencement of the dorsal. 
Snout rather pointed. Jaws equal, their outer surface smooth, but crenated on their cutting 
edges. No spinous canines at the corners of the mouth. Eyes rather small, their diameter not 
one-fifth the length of the head, situate above the middle of the cheek, but equidistant from the 
posterior lobe of the opercle and the extremity of the snout. Snout in front of the eyes, and 
* Freycinet Voyage, (Zoologie) p. 286. 
P 
