HAPLOCHITONID^. 651 



have been found occasionally on tlie ISTortb. British, and, more 

 frequently, on the Norwegian coast. The other species are 

 from the Mediterranean. Attaining to a length of 18 inches. 



Sixteenth Family — PEECopsiDiE. 



Body covered with ctenoid scales ; head naked. Margin of 

 the upper jaio formed hy the intermaxillaries only ; operenlar 

 apparatus complete. Barhels none. Gill - openings wide. 

 Adipose fin present. 



One genus and sj^ecies only (Percopsis guttatus) ; interest- 

 ing as having the general characters of Salmonoids, but the 

 mouth and scales of a Percoid. Freshwaters of the northern 

 United States. 



Seventeenth Family — Haplochitonid^. 



Body naked or scaly {cycloid). Margin of the tcppcr Jaw 

 formed by the iritermaxillary ; opercular apparatus complete. 

 Barhels 7ione. Gill - opening wide ; pseudobranchice. Air- 

 bladder simple. Adipose fin present. Ovaries laminated ; the 

 eggs fall into the cavity of the abdomen, there being no oviduct. 

 Pyloric appendages none. 



Freshwater-fishes which represent the Salmonoids in the 



Fig. 296. — Prototroctes oxyrliyuclius, New Zealand. 



southern hemisphere. Two genera only are known. Hap- 

 lochiton (Fig. 104, p. 250) abundant in lakes and the streams 



