NORTH PACIFIC OPHIURANS IN NATIONAL MUSEUM CLARK. 7 



courtesies in the preparation and publication of tliis report I am 

 indebted to the National Museum, and for many helpful suggestions 

 to Doctor Rathbun and Miss Mary J. Rathbun. 



THE DISTRIBUTION OF THE NORTH PACIFIC OPHIUROIDEA. 



Doubtless the most interesting result of the study of the mass of 

 material which has just passed through my hands is found in the 

 light which it throws on the distribution of the species of opliiuran« 

 with reference to the shore lines, to the depth and temperature of the 

 water, and to each other. 



GEOGRAPHICAL DISTRIBUTION. 



The great bulk of the collection is made up of species from southern 

 japan, no less than 112 of the 189 species (60 per cent) being nearly 

 or cjuite confined to that region, at least so far as the present collection 

 reveals their distribution. As a good example of this group may be 

 cited Ophiura sterea, which was taken at fourteen stations on both 

 the eastern and western coasts of Japan as far north as 38°. On the 

 eastern coast few of these 112 southern species extend beyond lat. 

 38° N. and most of them seem to find their northern limit in or near 

 Sagami Bay. On the western coast, however (i. e., in the Sea of 

 Japan), they apparently extend somewhat farther north, as far as 

 Tsugaru Strait (nearly 42°) and occasionally farther, even beyond 

 the forty-third parallel. Yet nearly one-third of the 112 southern 

 species were not taken on either coast north of the thirty-third par- 

 allel and do not appear to enter the Sea of Japan nor to extend up 

 the east coast of Honshu Island. A large group of species which do 

 not extend into the Sea of Japan do follow the southeastern coast of 

 the islands as far as Suruga Gulf. On the other hand, there are very 

 few species which occur in the Sea of Japan which do not also occur 

 in Suruga Gulf or Sagami Bay, so that the ophiuran fauna of the Sea 

 of Japan is apparently, far less varied than that of the Pacific shores 

 of Honshu, Shikoku, and Kiusiu islands. There can be no question 

 that this very rich ophiuran fauna of southern Japan is closely allied 

 to the still richer East Indian fauna, although it is far from identical 

 with it, for scarcely a dozen of the 112 species comprising the Japa- 

 nese fauna have yet been taken in the East Indian region. While 

 there is little reason to doubt that further collecting will show a 

 much larger number of species common to the two regions, it seems 

 both proper and desirable to recognize the assemblage of species 

 around southern Japan as a distinct group, which we may conven- 

 iently call the Honshu fauna. 



Aside from this Honshu fauna, the largest assemblage of species 

 from a given district is shown at the opposite extreme of the iirea 



