NORTH PACIFIC OPHIURANS IN NATIONAL MUSEUM CLARK. 



15 



There are two species the depth of whose habitat is not known, but 

 the remainder of the collection, fifty-five species in all, were taken in 

 water less than 50 fathoms deep, and may fairly be considered littoral 

 forms. Of these no less than thirty-four are known to extend their 

 range beyond 50 fathoms, twenty-eight beyond 100, twelve beyond 

 300, seven beyond 500, four beyond 800, and two even pass the 

 1,000-fathom line. The temperature range can not be given because 

 there are no temperature records for most of the shallow-water sta- 

 tions, but as Ophiopholis aculeata was taken at the extraordinarily 

 low temperature of 29.8, it is more than likely that the temperature 

 range for the group exceeds 50. The extreme range for any one 

 species is 33.8. 



It will be noted that of the 187 species whose bathymetrical range 

 is known, 146, or nearly 80 per cent, are distinctly shallow-water 

 forms, having been taken at less than 300 fathoms. Of these 146 

 species, 55, or 38 per cent, extend their range be}^ond 300 fathoms, 

 while 35, or 24 per cent, are not recorded from below 100 fathoms. 

 Of the forty-one species not taken in less than 300 fathoms, thirty- 

 one occur below 500 fathoms. Of these really deep-water species, 

 twelve belong to the genus Ophiacantha, six to Ophiura, and three 

 to OpMomitra. The remainder represent ten different genera, of 

 which the following four may fairly be considered characteristic of 

 the abyssal region : 



Anthophiura. 



Ophiotrochus. 



Ophiambix. 



Amphilepis. 



The following eight species have a bathymetrical range of more 

 than 1,000 fathoms: 



With this group belong the following trio, whose range, however, 

 is not quite so extensive: 



