32 ACANTHOPTEEYGII. 



portion being usually considerably shorter than the posterior soft-rayed one ; (2) the 

 presence of only one or two anal spines ; and (3) the toothless palate. 



One permanently fluviatile species (Rajiloidonotus grunniens) is found in the rivers 

 of Mexico and Central America, but whether any of the Scia3nid shore-fishes of this 

 region ascend rivers above the influence of the tides is uncertain *. 



HAPLOIDONOTUS, Rafin., 1819. 



Aphdinotm, Jord. & Everm. Bull. U.S. Nat. Mus. xlvii. 1898, p. 1484. 



Body rather deep, compressed. Mouth subterminal ; no barbels ; prajmaxillaries protractile ; maxillary 

 concealed by the prseorbital ; no supramaxillary ; jaws with bands of small pointed teeth; palate 

 toothless ; lower pharyngeals large, completely united, with molariform teeth ; prseoperculum weakly 

 denticulated. Scales of moderate size, ciliated ; lateral line curved anteriorly, continued nearly to the 

 end of the caudal fin. A single dorsal, scaly at the base, with X 29-32 rays ; anal with II 7 rays ; 

 caudal doubly truncate ; pectoral asymmetrical, pointed ; ventrals each of a spine and 5 branched rays, 

 inserted a little behind the base of the pectorals, without scaly axillary processes. 



1. Haploidonotus grunniens, Eafin., 1819. 



Corvina oscula, Giinth. Cat. Fish. ii. p. 297 (1860). 



Aplodinotus grunniens, Jord. & Everm. Bull. U.S. Nat. Mus. xlvii. 1898, p. 1484. 



Depth of body 2| to 24 in the length, length of head 3^ to 3|. Back elevated, the ventral profile being nearly 

 straight. Snout short, obtuse ; maxillary extending to below posterior part of eye, the diameter of which 

 is about 5 in the length of head and 1| in the interorbital width. Scales 56-62 ^^. Dorsal X 29-32 ; 

 spines moderately strong, the third highest, i the length of head and nearly as long as the longest 

 branched rays. Anal II 7 : second spine strong, about as long as the longest dorsal spine, shorter than 

 the anterior branched rays. Pectoral as long as the head. Silvery, back darker ; vertical fine dusky. 



Ilah. Rivers and lakes of North America, from the Great Lakes to Chiapas (in Mexico 

 recorded from Matamoros in Tamaulipas and the Rio Usumacinta). 



This species, here described from Winnipeg examples of from 250 to 300 mm., 

 attains a weight of 50 or 60 pounds. 



Pani. 7. PERCIDiE. 



The Percidfe are a large family inhabiting the fresh waters of North America and 



Western Eurasia. The majority of the American species are the small fishes known 



as " darters," a few of which occur in Northern Mexico. These belong to two very 



closely allied genera, Fercina and Etheostoma, which may be distinguished from other 



Perciform fishes by the following diagnosis : — 



Body more or less elongate and compressed. Mouth smaller moderate ; praBmaxillaries not protractile, except 

 at the sides ; maxillary exposed, but slipping under the pra3orbital for the whole length of its upper edge ; 

 villiform teeth in the jaws and usually on the palate. Scales small, denticulated. Two dorsals, with 



* In the British Museum are examples of Bairdiella icistia, .lord. & Gilb., and Ci/noscton xanthulas, Jord. & 

 Gilb., collected by Ilcrr Forrer in the Itio Presidio, but probably near the mouth of the river. 



