282 FISHES. 



south. But tlie truly tropical forms are absent ; there are iio 

 Squamvpinnes, scarcely any Mullidce, no Acronuri, no Teutliyes, 

 no PomacentridoR (with a single exception on the coast of 

 Chih), only one genus of Julidina, no Scarina, which are re- 

 placed by another group of Pharyngognaths, the Odacina. 

 The Labrina, so characteristic of the temperate zone of the 

 Northern Hemisphere, reappear in a distinct genus {Malaco- 

 pterus) on the coast of Juan Fernandez. 



The family of Berycidce, equally interesting with regard to 

 their distribution in time and in space, consists of temperate 

 and tropical genera. The genus by which this family is 

 represented in the southern temperate zone {Trachichihys) is 

 much more nearly allied to the northern than to the tropical 

 genera. 



The true Cottina and Heterol&pidina (forms with a bony 

 stay of the prseoperculum, which is generally armed) have not 

 crossed the tropical zone ; they are replaced by fishes ex- 

 tremely similar in general form, and having the same habits, 

 but lacking that osteological peculiarity. Their southern 

 analogues belong chiefly to the family Trachinidce, and are 

 types of genera peculiar to the Southern Hemisphere. 



The Discoholi of the ISTorthern Hemisphere have likewise 

 not penetrated to the south, where they are represented by 

 Goiiesocidce. These two families replace each other in their 

 distribution over the globe. 



Nearly all the Pleuronectidce (but they are not numerous) 

 belong to distinct genera, some, however, being remarkably 

 similar in general form to the northern Pleuronedes. 



With Gadoids Myxinidce reappear, one species being ex- 

 tremely similar to the European Myxine. Bdellostoma is a 

 genus peculiar to the southern temperate zone. 



As in the northern temperate zone, so in the southern, 

 the number of individuals and the variety of forms is much 

 less than between the tropics. This is especially apparent 



