144 BULLETIN 82, UNITED STATES NATIONAL MUSEUM 



In the occurrence of a syzygy between the elements of the IBr series and in the 

 plating of the disk the Eudiocrinidae agree with the Zygometridae. These two 

 families also agree in the structure of the articular faces of the radials, the agreement 

 between Eudiocrinus (see Part 2, p. 22, figs. 29, 30, p. 20) and Catoptometra (see Part 

 2, p. 21, figs. 32, 33, p. 20) being especially close. In those species of Zygometridae 

 in which adambulacral deposits are found in the lateral perisome of the pinnules these 

 deposits are of the type characteristic of the Eudiocrinidae, although they are more or 

 less reduced. 



In the Eudiocrinidae the disk is more heavily plated than it is in the Zygometridae, 

 the adambulacral rods are always large, and there are large filmy plates over the 

 gonads. It may be remarked that in the genus Mariametra of the family Mari- 

 ametridae the disk is always well plated, although there are no other features to 

 suggest affinity with the Zygometridae or Eudiocrinidae. 



The Zygometridae and the Eudiocrinidae, though quite distinct, possess in com- 

 mon a number of features that clearly indicate a rather close relationship and at the 

 same time set them off rather sharply from the 3 other families in the Mariametrida 

 the Himerometridae, Mariametridae, and Colobometridae which similarly are 

 closely allied. 



History. The family name Eudiocrinidae was first proposed by me in 1907 to 

 include the genera Eudiocrinus and Decametrocrinus. The genus Eudiocrinus was 

 accepted in the sense in which it was used by Carpenter that is, as including the 

 species now assigned to it and also the species now referred to Pentametrocrinus. 

 At that tune I had at hand many specimens of Carpenter's Eudiocrinus (Penta- 

 metrocrinus) varians and E. (P.) japonicus, which I had collected in southern Japan 

 in the previous year, but I had never seen a specimen of Eudiocrinus indivisus or of 

 any closely related species. My concept of the genus Eudiocrinus was therefore 

 based entirely on species of Pentametrocrinus, and the family Eudiocrinidae as proposed 

 was in intent the equivalent of the family Pentametrocrinidae as now understood. 



Shortly after the publication of this paper I acquired a specimen of a species 

 related to Eudiocrinus indivisus the type specimen of E. variegatus and a study of 

 this individual showed that the group of species represented by E. indivisus is entirely 

 different from the group represented by E. varians and E. japonicu^. In a paper 

 published on April 11, 1908, I established the new genus Pentametrocrinus for E. 

 varians and its allies and created the new family Pentametrocrinidae for the reception 

 of Pentametrocrinus and Decametrocrinus. I showed that Eudiocrinus, as represented 

 by E. indivisus, is characterized by the possession of IBr series of which the IBr 2 is not 

 axillary, which are wholly unrepresented in E. varians and its allies (the genus 

 Pentametrocrinus), and that it is most closely related to the genus Zygometra. I 

 therefore created the new family Zygometridae to include the genera Zygometra 

 (which at that tune included also Catoptometra) and Eudiocrinus. 



In a paper published later hi the same year (May 14), but written before the 

 receipt of the type specimen of Eudiocrinus variegatus, the family Eudiocrinidae 

 appears as including Eudiocrinus and Decametrocrinus, and the family Zygometridae 

 as including Zygometra only. 



Until the present time the genus Eudiocrinus has remained hi the family Zygo- 

 metridae to which it was assigned in 1908. 



