176 MALACOPTEEYGII. 



Sub-order VIII. MALACOPTERYGII. 



This sub-order is represented in the fresh waters of Mexico and Central America by 

 a few fishes, mostly marine types. These are soft-rayed fishes with elongate or ovate 

 scaly body and naked head ; dorsal, anal, and caudal fins are present, the pectorals are 

 placed low and the ventrals are abdominal. The naked head, the maxillary forming 

 part of the border of the mouth, the normal position of the lateral line (when present), 

 and the larger number of rays in the ventral fins distinguish them externally from the 

 Haplomi of this region. From the Characinidse they may usually be distinguished by 

 the larger number of branchiostegal rays. 



Si/nojjsis of the Families represented in the fresh loaters of Mexico 



and Central America. 

 I. An adipose dorsal fin 1. Saljionid.e. 



II. No adipose fin. 



A. No gular plate ; teeth small or absent. 



No lateral line 2. Clupeid.e. 



Lateral line well developed 3. Chanid.e. 



B. A gular plate between the rami of the lower jaw ; bands of villiform teeth 



iu the jaws and on the palate and tongue 4. Elopid^. 



Fam. 1. SALMONID^. 



The Salmonidge are principally a circumpolar family of marine origin which are 

 establishing themselves in fresh water in the Palcearctic and Nearctic Regions. One 

 fresh-water genus occurs in Australia and New Zealand. There are about twenty 

 genera, but the number of species which should be recognized is very uncertain. 



1. SALMO, Linn. 



Oncorhynchus (Suckley, 1861) and Salmo, Jord. & Evcrm. Bull. U.S. Nat. Mus. xlvii. 1896, 

 pp. 474 and 483. 



llody elongate, more or less compressed, covered with small cycloid scales. Lateral line present. Head 

 naked ; mouth large ; conical teeth in the jaws and on the palate. Dorsal fin short, in the middle of the 

 length of the fish ; an adipose fin ; anal short or of moderate length ; caudal forked or truncate. 



The species are very variable and difficult to define; they inhabit the rivers and 

 ■ lakes of North America, Europe, and Asia; many of the forms are migratory, living 

 part of their life in the sea and ascending rivers to spawn. 



1. Salmo clarkii, llichards. 



Salmo mykiss, Jord. & Everm. Bull. U.S. Nat. Mus. xlvii. 1896, p. 487. 



Salmo clarkii, Jord. & Evcrm. t. c. 1900, p. 3819. 



Salmo irideus, Meek, Publ. Columhian Mus., Zool. v. 1901, p. 96. 



