A MONOGRAPH OF THE EXISTING CRINOIDS 143 



Thermal range. One record, 11.67 C. 



History. This species was described originally under the name of Antedon 

 hartlaubi in 1907 from a specimen dredged by the Albatross in the Korean Straits in 

 1906. Later hi the same year another young individual from Albatross station 3717 

 in Sagami Bay was described as Zygometra koehleri. In 1918 in the report upon the 

 Siboga collection koehleri was placed in the synonymy of hartlaubi. 



In 1922 Dr. Torsten Gislen described in detail a specimen which had been 

 collected by Dr. Sixten Bock off Kagoshima, and in 1927 he described another from 

 Dr. Th. Mortensen's collection, which apparently was taken at the same time and 

 place. 



Family EUDIOCRINIDAE A. H. Clark 



Eudiocrinidae A. H. CLARK, Smithsonian Misc. Coll., vol. 50, 1907, p. 344 (in part; new family to 

 include Eudiocrinus and Decametrocrinus); Proc. Biol. Soc. Washington, vol. 21, 1908, p. 135 

 (name replaced by Pentametrocrinidae, the genus Eudiocrinus being transferred to the Zygo- 

 metridae); Proc. U. S. Nat. Mus., vol. 34, 1908, p. 210 (in part; in key; includes Eudiocrinus 

 and Decametrocrinus; range), p. 211 (represented in Hawaiian Islands), p. 212 (range of com- 

 ponent genera); Rec. Indian Mus., vol. 34, pt. 4, 1932, p. 554 (including Eudiocrinus only); 

 Temminckia, vol. 1, 1936, p. 300; John Murray Exped. 1933-34, Sci. Reports, vol. 4, No. 4, 

 1936, pp. 99, 103. 



Zygometridae (part) A. H. CLABK, Proc. Biol. Soc. Washington, vol. 21, 1908, p. 135 (includes 

 Zygometra and Eudiocrmus) . [For subsequent references see page 76.] 



Diagnosis. A family of the superfamily Mariametrida in which the elements of 

 the IBr series are united by syzygy and the IBr 2 is not axillary, but bears a pinnule, 

 the arms being therefore only five in number. The perisome of the disk is completely 

 covered by a pavement of irregular plates (see Part 2, p. 226, fourth paragraph), and 

 the lateral perisome of the pinnules contains an inner and an outer row of spicules 

 (see Part 2, p. 238, and figs. 787 and 788, p. 366). 



Geographical range. From the Maldive Islands, Cape Negrais, Burma, and the 

 Andaman Islands to the Lesser Sunda and Kei Islands, the Moluccas, the Philippine 

 and Bonin Islands, and southern Japan. 



Bathymetrical range. From 36 to 183 meters. 



Remarks. The possession of only five arms easily distinguishes the species of the 

 family Eudiocrinidae from all other comatulids except the species of Pentametrocrinus 

 in the family Pentametrocrinidae and the species of Atopocrimifs in the family Atele- 

 crinidae of the suborder Macrophreata (see Part 5). 



In the Eudiocrinidae the first two postradial ossicles are the equivalent of the IBr 

 series in comatulids with 10 or more arms, but the IBr 2 is not axillary, simply bearing 

 a pinnule. The third postradial ossicle is the equivalent of the first brachial of the 

 free undivided arms in other comatulids, and consequently does not bear a pinnule. 

 In the Pentametrocrinidae the IBr series are absent, the first ossicle following the 

 radials representing the first brachial of the free undivided arms in other comatulids. 



It is interesting that in the Eudiocrinidae the sequence of the pinnules is that seen 

 on the free undivided arms in other comatulids that is, P c and P, are similar, forming 

 the first pair; P a and P 2 are similar, forming the second pair; and so on whereas it 

 might be expected that the pinnule of the IBr series (P c ) would be an odd pinnule 

 and that the grouping of the pinnules in pairs would commence with PI as is the case 

 in other comatulids with pinnules on the division series. 



