Vol. XXII, pp. 1-22 January 9, 1909 



PROCEEDINGS 



OF THE 



BIOLOGICAL SOCIETY OF WASHINGTON 



A REVISION OF THE CRINOID FAMILIES THALAi^S,Q 

 METRID.E AND HIMEROMETRID^E. 



BY AUSTIN HOB ART CLARK. 



In my first revision of the unstalked crinoids (Smiths. Mis- 

 cell. Coll., Quarterly Issue, l, pp. 343-364; Bull. Mus. Comp. 

 Zool., LI, No. 8, p. 245), I was, through lack of material, unable 

 to arrive at a true understanding of the interrelations of the spe- 

 cific groups which I called collectively Antedon, and various other 

 groups which I segregated into the "genera" Himerometra, 

 Thalassometra , and Charitometra. These genera were sufficiently 

 definite and well marked to serve as units, and I therefore had 

 no hesitation in considering them as such until further material 

 was available upon j^vhich to base a more detailed study. This 

 was soon possible in the case of ' ^ Antedon ,' ' and that genus was 

 promptly resolved into its component specific groups (these 

 Proceedings, xxi, pp. 125-136) ; but the other genera, from a 

 lack of adequately representative material, proved more difficult; 

 of ''Himerometra^^ especially, I was only acquainted with a very 

 small proportion of the very numerous species. The receipt of 

 a very interesting collection from the Hawaiian Islands, and of 

 the extensive Japanese collection deposited by Mr. Frank 

 Springer threw considerable liglit on a number of hitherto obscure 

 points in regard to '' I'halassovietra " and ''Charitometra"; more 

 recently, through the kindness of Dr. Th. Mortensen, I have been 

 able to study the magnificent collection belonging to the Univer- 

 sity of Coj^enhagen, and the U. S. Bureau of Fisheries has 

 entrusted to me the collections made by the steamer Albatross 

 among the Philippine Islands, so that I now have been able to 

 examine all of the important types referred to Himerometra. 



The new genera described herein are based upon obvious 

 external characters, in order that they may be readily recognized 

 1— Prog. Biol. Soc. Wash., Vol. XXII, 1909. (1) 



