THE APODOTJS HOLOTHTJBIANS 133 



sentatives of seven genera, of which four (two monotypic) are really charac- 

 teristic. The Arctic region is characterized by the three genera (two mono- 

 typic) of Myriotrochinae, and three other genera are represented there. The 

 Antarctic region has two characteristic genera, while four other genera occur 

 there. No synaptids are known from the West American region or the Guinea 

 subregion, and there are no characteristic genera in the East American region 

 nor in either the Mediterranean or Pacific Boreal subregions. One genus, 

 Chiridota, cannot be considered characteristic of any single region ; of all synap- 

 tid genera it is the most truly cosmopolitan. As regards the abyssal region (over 

 1,000 m.), Protankyra, Chiridota, Myriotrochus, and Acanthotrochus are repre- 

 sented there, but the two latter are characteristically Arctic forms and only ex- 

 tend a little way into the Boreal subregions, so that we are justified in saying 

 that the only truly abyssal Synaptids known are a few species of Protankyra and 

 Chiridota. The following table will show these facts of distribution in a conven- 

 ient way. The * indicates that the genus is characteristic of the region, ** that it 

 is not found elsewhere, and the figures in parentheses indicate the number of 

 species occurring in that region. 



Indo-Pacific Littoral Region: Atlantic Boreal Subregion (continued) : 



Euapta (1). **Toxodora (1). 



** Opheodesoma (4). Protankyra (1). 



* * Poly plectana (.1 ) . Chiridota ( 1 ) . 



** Synapta (1). Myriotrochus (2). 



* Synaptula (7). Arctic Circumpolar Subregion: 



* Protankyra (17). * Myriotrochus (2). 



* Anapta (2). ** Trochoderma (1). 



t * * Dacty lapta ( 1 ) . * * Acanthotrochus ( 1 ) . 

 ** Polycheira (1). Leptosynapta (1). 



** Achiridota (1). Labidoplax (1). 



* * Scoliodota ( 1 ) . Chiridota ( 2 ). 



Chiridota (6). Pacific Boreal Subregion: 

 Leptosynapta (1). Leptosynapta (1). 



Labidoplax (1). Chiridota (1). 



Tseniogyrus (1). Myriotrochus (1). 



Antarctic Littoral Region: East American Littoral Region: 



* Taeniogy rus ( 2 ) . Euapta ( 1 ). 

 *Trochodota (2). Synaptula (1). 



Leptosynapta (1). Leptosynapta (3). 



Anapta (1). Chiridota (1). 



Chiridota (3). Mediterranean Subregion: 

 Scoliodota (1). Leptosynapta (2). 



Atlantic Boreal Subregion: Labidoplax (2). 



* Leptosynapta (7). Trochodota (1). 



* Labidoplax (4). Abyssal Region: 



** Rhabdomolgus (1). Protankyra (7). 



Chiridota (2). 



