slowly in lines parallel to the direction of that motion as far 

 as the conditions permitted. 



The extension of the species of the genus Florometra from 

 the Magellanic region to Alaska, the western Aleutian Islands 

 and southern Japan indicates an unbroken continuity of 

 physical and economic conditions at the depth at which 

 these species live, and these conditions are not quite the 

 same as those in the abysses, into which the species do not 

 descend. 



The difference, however, is an economic and not a physical 

 one, for the water in which these species live does not, so far as 

 can be seen, differ in temperature or in salinity to any extent 

 from the abyssal w T ater. 



The species of Florometra are all of large size, being, in 

 fact, among the largest of the recent crinoids ; they therefore 

 require a large amount of food; that is, they must exist in or 

 beneath water carrying a relatively large amount of plankton. 

 Therefore where a strong current exists parallel to the coast, 

 preventing the diffusion of the water, loaded with inorganic 

 material, from the land and restricting it to a narrow belt along 

 the shore, the species will be restricted to the region below this 

 narrow belt of shore water, and to that portion of the current 

 adjacent to it, and will consequently have a small bathymétrie 

 range. When the current slackens, allowing the coastal water 

 to become more widely diffused, these crinoids will at once 

 increase the breadth of the coastal strip which they inhabit, and 

 consequently also their bathymétrie range. If in any locality 

 there is a seasonal motion of water perpendicular to the coast, 

 whereby the littoral water becomes widely diffused over the 

 ocean, in such a locality the coastal strip inhabited by these 

 crinoids, and their bathymétrie range, will at once become very 

 great. 



• True abyssal crinoids are all very small, with very large 

 mouths. The great development of the digestive system enables 

 them to subsist upon food with a maximum of waste and a 

 minimum of nutritive value, such as falls upon them in the 

 deep sea; but the species of Florometra are typical littoral 



(285) 



