276 FISHES 



when we consider that the two regions are at present in 

 communication along the Arctic coasts and have been also 

 connected in comparatively recent geological periods through 

 the Isthmus of Panama, which is believed on geological evi- 

 dence to have been depressed below the sea-level at the end of 

 the Eocene period. The most remarkable peculiarity of the 

 region is the presence of the family Embiotocidre or surf-perches, 

 allied to the wrasses ; all but two of the species occur on the 

 Pacific coast of North America, the two exceptions being found 

 on the coasts of Japan. No Embiotocidae are found in any 

 other part of the world. True wrasses (Labridae) also occur 

 both on the east and west coasts of this region as well as repre- 

 sentatives of the parrot-wrasses (Scaridae). Another family 

 peculiar to the region is that of the Hexagrammida; allied to 

 the Scorpoenidae, some of the genera being remarkable for the 

 possession of several lateral lines, and all having only a single 

 nostril on each side ; they live on both sides of the region and 

 are known in America as greenlings. Scorpaenidae themselves 

 are abundant, especially species of the viviparous genera Sebas- 

 todes and Sebastichthys, viviparous reproduction being a char- 

 acteristic feature of the Pacific coast. The European mackerel,. 

 Scomber scombrus, is absent, but the smaller and less valuable 

 .S. colzas is abundant on the coasts both of California and Japan. 

 The tunny is also fairly abundant. Carangidse or horse- 

 mackerels are represented by species of Caranx, Trachurus, and 

 Seriola or yellow-tail. Most of the other families of Acan- 

 thopterygii are represented, though usually by species distinct 

 from those of the Atlantic. Of the Gadidns, which are less 

 numerous than in the Atlantic, there is a cod, Gadus macroce- 

 phalus, only slightly different from the Atlantic species, two 

 species resembling the pollack, and called Theragra, and a small 

 form called tom-cod, Microgadus. The Pleuronectidae are well 

 represented, the halibut is abundant, and there are several 

 other allied species referred to different genera ; the flounder, 

 plaice, dab, merry sole, and pole dab are all replaced by 

 representative species ; soles are extremely scarce, only a 

 few species allied to Achirus occurring in Japan. Of the 

 Clupeidae the principal are Clupea pallasi, as abundant as the 

 herring in the Atlantic, and Sardi?iellct caerulea, the Cali- 

 fornian sardine. Salmon are more abundant in the North 



