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. Rows 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. 

 Colour. — " 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 Labridce, but having evidently very strong 

 affinities to some of the Scicenidce. 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. 

 Plate XXI. 

 S. eerughwso cyaneus, capite et pinnis flavo-vittatis : maxillis exteriiis Icevibus, mar- 

 ginibus crenatis ; caninis ad angulos oris nullis : f route gradatim proclivi: lined 

 laterali lubis parum ramosis : squamis ubique striato- granulatis : pectoralibus acu- 

 minatis, radiis superioribus arcuatis : caudali radiis ex terms cceteris longioribus, 

 acuminalis. 



D. 9/10 ; A. 3/9 ; C. 13. &c. ; P. 15 vel 16 ; V. 1/5. 

 Long. nnc. 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 



