IIAI'I.OCHITON. 381 



Fam. 3. HAPLOCHITONIDvE. 



Body naked or scaly. Margin of the upper jaw 

 formed by the intermaxillary ; opercular apparatus 

 complete. Barbels none. Gill-opening wide ; pseudo- 

 branchioe well developed. Air-bladder simple. Adi- 

 pose fin present. Ovaries laminated ; the eggs fall 

 into the cavity of the abdomen, there being no ovi- 

 duct. Pyloric appendages none. 



Freshwater fish from the temperate parts of South America and 

 South Australia, representiug the Salmonoids of the northern hemi- 

 sphere. 



Only two genera are known, which, perhaps, will become the types 

 of two distinct groups when we shall be better acquainted with the 

 Australian form. 



Body naked 1. Haplochiton, p. 381. 



Body scaly 2. Prototrocte.s, p. 382. 



1. HAPLOCHITON. 



Aplochiton, Jenyns, Voy. Beagle, Fish. p. 130. 

 Farionella, Cuv. ^- Val. xxii. p. 507. 



This genus has the general habit of the Trout, but is completely 

 naked. The dorsal fin occupies a position somewhat posterior to 

 that of the ventrals, which are in the middle of the length of the 

 body, and composed of seven rays. Adipose fin small ; caudal forked ; 

 anal of moderate length. The nostrils are somewhat remote from 

 each other. Eye of moderate size. Teeth small, curved, in a single 

 series, in the upper and lower jaw and on the palatine bones. 

 Tongue broad, with a series of curved teeth on each side. Gill- 

 openings rather wide, the gill-membranes not attached to the 

 isthmus ; the outer branchial arch with lanceolate gill-rakers. Pseudo- 

 branchia) well developed. Air-bladder simjjle, grown to the walls 

 of the abdomen. Stomach thick and muscular ; pyloric appendages 

 none. Tlie urogenital orifice of both sexes is produced into a cylin- 

 drical tube, which lies concealed in a groove before the anal fin. 



Tierra del Fuego and Falldand Islands. 



1. Haplochiton zebra. 



Aplochiton zebra, Jenyns, Voy. BeayU; Fi.^'ft. p. 131. pi. 24. tig. 1. 

 Farionella gayii, Cuv. <§• Val. xxii. p. 508. pi. 049 (not good). 



B. 3. D. 12-13. A. 15-16. V. 7. Vert. 45/22. 



The height of the body is somewhat more than one-fifth of the 



