724 



THE AMERICAN NATURALIST 



[Vol. XLII 



unrivaled among the marine invertebrates. Observers 

 have contented themselves with making short color notes, 

 each on a very limited number of species, and no one has 

 as yet made this phase of the subject an object of study, 

 yet there appear to be many interesting points well 

 worthy of record. 



All colors are found in the crinoids except blue, though 

 true black is confined to the disks of the Pentametro- 

 crinidae and to lines and spots on two species of Cocco- 

 metra, and may therefore be omitted from a general dis- 

 cussion. Both blue and black, however, enter largely 

 into combinations. 



Yellow is the commonest color in the group, and is the 

 color of all the more primitive forms, and of the young 

 of almost all the others; it may, therefore, be taken as 

 the fundamental basic crinoid color. The pentacrinoids 

 of Antedon bifida are sometimes pink, though usually, 

 like the pentacrinoids of the other forms in which they 

 are known, yellow, and certain other forms are dull pinkish 

 at all stages. We may, therefore, assume two basic colors, 

 yellow and red, the latter an intensification of the former, 

 found generally in the more speeialized forms. 



The derivatives from these two basic colors as they 

 occur in the crinoids may be grouped as follows : 



Under the first heading come : 



Yellow: Bathycrinus, Khizocrinus, Ptilocrinus, Phryno- 

 crirnis, Xanometra, Adelometra, Trichometra, Heliometra, 

 Atelecrinus, and all but very large specimens of the 

 species of ThalassometridcT. 



White: Asterometra; markings on shallow water 



IT. Red 



J + [Blue] 

 ( + [Black] 



f Purple? 

 \ Violet. 



Thalassometrida 



[athrometra, Coccometra, Leptometra, Comp- 



