28 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. "^2 



After the full size has been reached a dusky factor makes its 

 appearance which may be generally diffused or more or less localized, 

 and deepens, alters, or obscures the original colors. 



Illumination of the habitat results in an intensification of the natural 

 colors and the very early appearance of the dusky age factor, as well 

 as in the appearance of a blue factor resulting in the formation of 

 bright greens, purples and violet, which may deepen to black. 



All the comatulids living below the limit of light penetration exhibit 

 the basic colors, white, orange or red, only, which, though they may 

 become more intense toward the calyx and arm bases, are never other- 

 wise diversified. Each of these colors, however, may be modified by 

 the dusky age factor, resulting in " dusky purple," greenish or brown- 

 ish yellow, brown, orange brown, crimson, or red brown. The blue 

 factor is absent in these species, but in the group as a whole it gradu- 

 ally increases from the limit of light penetration to the surface, 

 causing the appearance of greens, purples and violets of increasing 

 intensity. 



Geographically the maximum development of color diversity ap- 

 pears to be in the Malayan and north Australian region, and thence 

 westward to Ceylon; but it is here also that the maximum develop- 

 ment of littoral types is found. The whole littoral and intermediate 

 fauna from east Africa to Oceania and southern Japan is notable for 

 the diversity in the coloration of the endemic forms. 



On the other hand, throughout the vast extent of the east and north 

 Pacific we find the minimum diversity of crinoid coloration ; all of 

 the comatulids are unicolor, most of them yellow, becoming yellow 

 brown, a few purplish brown or red ; all of the stalked forms are 

 yellow. 



The crinoids of the Caribbean Sea as we know them to-day are 

 much less highly colored than those of the Indo-Pacific region, and 

 this holds good for stalked as well as for unstalked types. But here 

 the groups which furnish the majority of the most variegated species 

 are absent. In the remaining portions of the Atlantic, outside of the 

 region of the Cape of Good Hope where the Indo-Pacific fauna in- 

 trudes for a short distance, we note especially the presence of the 

 highly colored species of Antcdon, which range collectively from Rio 

 de Janeiro to St. Thomas and from the Gulf of Guinea to Norway, 

 including the Mediterranean basin ; of the green or white species of 

 Leptometra which occur from Madeira to Scotland, including the 

 Mediterranean basin ; and of the small green or gray species of 

 Hathrometra which are found from Chesapeake Bay and Portugal 

 northward. 



