12 ZOOLOGY OF THE VOYAGE OF THE BEAGLE. 



Colour. — The specimen above described appears, in its present state, greyish brown, with zig-zag 

 lines in different directions of a darker tint. A second individual is stated by Mr. Darwin to 

 have been, when alive, " above salmon-coloured." A third is described as " above aureous- 

 coppery, with wave-like lines of dark brown, which often collect into four or five transverse 

 bands ; fins lead-colour ; beneath obscure ; pupil dark blue." Both these last specimens appear 

 now, like the first, greyish-brown. The wave-like lines extend over a portion of the dorsal and 

 anal fins. 



Habitat, coast of Northern Patagonia, and the mouth of the Plata. 



This species is evidently very closely allied to the P. Brasilianum of Cuvier 

 and Valenciennes, and possibly may not be distinct. It differs, however, in having 

 only two, instead of three, teeth on the basal margin of the preopercle, which 

 character prevails in all the specimens. It has also one or two more soft rays in 

 the anal. It likewise approaches the P. aculeatum of the same authors, but this 

 last species is said to be particularly characterized by three very sharp points on 

 the subopercle towards the lower angle, in the room of which, in the species 

 here described, there is only one small triangular flattened point, rather sharp in 

 two individuals, but in the third blunt, with the margin slightly crenated. The 

 colours too appear to be different. 



Mr. Darwin's collection contains three specimens, which do not materially 

 differ from each other. The largest, measuring fifteen inches in length, was taken 

 in forty fathoms water off the mouth of the Rio Plata. The two others, smaller, 

 and not exceeding nine, and seven and a half inches respectively, were got on the 

 coast of Patagonia in lat. 38° 20' : where it is stated that great numbers were 

 obtained, many exceeding a foot in length. In these smaller specimens the 

 canines are not so numerous or well developed as in the larger one. 



" One specimen when caught, vomited up small fish and a Pilummis. Was 

 tough for eating, but good." — D. 



DlACOPE MARGINATA. CuV. 

 Diacope marginata, Cm. et Vol. Hist, des Poiss. torn. ii. p. 320. 



Form. — Greatest depth of the body and length of the head equal, each being not quite one-third of the 

 entire length. Nape somewhat elevated, whence the profile falls very regularly in a slightly convex 

 line. The jaws appear equal when open, but when closed the upper one is a little the longest. 

 Teeth velutine, with four well-marked canines in the upper jaw, two on each side of the anterior 

 extremity, the outer one of which is longer than the inner. Opercle with two fiat blunt points. 

 Denticulations of the preopercle, particularly those at the angle below the notch, moderately 

 well developed. Tubercle of the interopercle prominent. There are scales on the cheeks and 

 pieces of the gill-cover, but none on the crown, snout, jaws, or suborbitals. The scales on the 



