02 



THE VOYAGE OF II. M.S. CHALLENGER 



Chorology of the Genus Dytaster. 



a. Geographical distribution: — 



Atlantic : Four species between the parallels of 40° N. and 40° S. 



Dytaster madreporifer and Dytaster exilis, var. carinata, off the 

 coast of North America. Dytaster biserialis, between Madeira 

 and the Azores. Dytaster exilis, var. gracilis, west of Tristan 

 da Cunha. Dytaster nobilis, off the coast of South America, east 

 of Buenos Ayres. 



Pacific : Two species between the parallels of 40° N. and 40° S. 



Dytaster spinosus, in the Mid-North Pacific, near the meridian of 

 180°. Dytaster exilis, off the coast of South America, between Valpa- 

 raiso and the Island of Juan Fernandez. Varieties of this species are 

 found in the North and South Atlantic, as noted above. 



Eastern Archipelago: Two species between the parallels of 10° N. and 10° S. 



Dytaster inermis, off the northern extremity of Celebes. Dytaster 

 eequivocus in the Arafura Sea, west of the Arrou Islands. 



/3. Bath y metrical range : 800 fathoms to 2650 fathoms. 



All the species are confined to the Abyssal zone — one only [Dytaster lequivocus) 



being found at a less depth than 1000 fathoms. 



Greatest range of one species : Dytaster madreporifer, 1240 to 1700 fathoms. 



Dytaster exilis, with its varieties, ranges from 1375 to 1900 fathoms. 

 y. Nature of the Sea-bottom: Four species — Dytaster inermis, Dytaster madreporifer, 



Dytaster nobilis, Dytaster exilis, var. carinata, are found on Blue mud. The 



type-form of Dytaster exilis and its variety gracilis are found on Globigerina ooze. 



Three species — Dytaster biserialis, Dytaster spinosus, Dytaster exilis, and Dytaster 



exilis, var. gracilis, are found on Globigerina ooze. Dytaster zequivocus is found 



on Green mud only, in 800 fathoms. 



