62 THE VOYAGE OF H.M.S. CHALLENGER. 
Chorology of the Genus Dytaster. 
a. Geographical distribution :— 
ATLANTIC: Four species between the parallels of 40° N. and 40° 8. 
Dytaster madreporifer and Dytaster exilis, var. carinata, off the 
coast of North America. Dytaster biserialis, between Madeira 
and the Azores. Dytaster ewilis, var. gracilis, west of Tristan 
da Cunha. Dytaster nobilis, off the coast of South America, east 
of Buenos Ayres. 
Paciric: 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° 8. 
Dytaster inermis, off the northern extremity of Celebes. Dytaster 
equivocus in the Arafura Sea, west of the Arrou Islands. 
6. Bathymetrical range. 800 fathoms to 2650 fathoms. 
All the species are confined to the Abyssal zone—one only (Dytaster xquivocus) 
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 imermis, 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 xquivocus is found 
on Green mud only, in 800 fathoms. 
Chorological Synopsis of the Species. 
Ocean. Range in Fathoms. Nature of the Sea-bottom. 
| 
Dytaster xquivocus . : . | Eastern Archipelago. 800 | Green mud. 
Dytaster biserialis . : . | N. Atlantic. 2025 Globigerina ooze. 
Dytaster exilis : : 2) |) Se baciies 1375 | Globigerina ooze. 
Dytaster exilis var. carinata . | N. Atlantic. 1700 | Blue mud. 
Dytaster exilis var. gracilis . | S. Atlantic, 1900 Globigerina ooze. 
Dytaster inermis. ‘ . | Eastern Archipelago. 2150 Blue mud. 
Dytaster madreporifer —. .-| N. Atlantic, 1240 to 1700 Blue mud. 
Dytaster nobilis . | 8. Atlantic, 2650 Blue mud. 
Dytaster spinosus. : . | N. Pacific. 2050 Globigerina ooze. | 
