160 BULLETIN 82, UNITED STATES NATIONAL MUSEUM 



lacking, the first two ossicles following the radials being the equivalent of the first 

 two ossicles following the IBr axillary in 10-armed forms. The species in which IBr 

 series are present although the IBr 2 is not axillary (variegatus and indivisus) I retained 

 in the genus Eudiocrinus, while those species that lack the IBr series altogether I 

 removed to the new genus Pentametrocrinus, assigning to this new genus the species 

 previously known as Eudiocrinus atlanticus, E. japonicus, E. semperi, E. tuberculatus, 

 and E. varians. 



The species was first described, and figures showing the lower pinnules and a 

 cirrus were given, in a paper written before that just mentioned, although it was not 

 published until June 20, 1908. In this paper a very detailed comparison of the struc- 

 ture of the species of Eudiocrinus and of those of Pentametrocrinus is given. 



In 1912 I published a description of a rather small and immature specimen without 

 locality that I had examined in the Hamburg Museum. 



EUDIOCRINUS VENUSTULUS A. H. Clark 



PLATE 12. FIGURES 45. 46 

 [See also vol. 1, pt. 2, fig. 191 (side view), p. 112.] 



Eudiocrinus venustulus A. H. CLARK, Proc. Biol. Soc. Washington, vol. 25, 1912, p. 27 (description; 

 Siboga station 289) ; Amer. Journ. Sci., vol. 40, 1915, p. 62 (listed) ; Unstalked crinoids of the 

 iStftoja-Exped., 1918, p. 65 (in key; range), p. 68 (references; detailed description; Stas. 289, 294; 

 Albatross station 5355), p. 275 (listed), pi. 17, figs. 27, 28. GISLEN, Nova Acta Reg. Soc. Sci. 

 Upsaliensis, ser. 4, vol. 5, No. 6, 1922, pp. 7, 73 (compared with E. loveni). -A. H. CLARK, 

 Temminckia. vol. 1, 1936, p. 295 (listed), p. 302 (Snellius station 60*; notes). 



Diagnostic jeatures. This small and slender species is readily distinguished from 

 all the other species in the genus by the large spatulate or fan-shaped process on the 

 first segment of P c . 



Description. The centrodorsal is thin-discoidal, with the bare dorsal pole flat, 

 finely papillose, 1.0 mm. in diameter. The cirrus sockets are arranged in a single 

 marginal row. 



The cirri are XII, 15-16, 6.5 mm. long, rather slender. The first segment is 

 short, the second is longer, the third is about as long as the median diameter, and the 

 fifth and sixth are the longest, about as long as the distal diameter or slightly longer. 

 The segments after the eighth are subequal, slightly longer than broad. The third- 

 seventh segments are constricted centrally with strongly expanded distal ends, which 

 overlap the bases of the succeeding segments, especially dorsally; beyond the seventh 

 this character gradually dies away. 



The distal border of the radials is just visible beyond the edge of the centrodorsal, 

 and is ornamented with a row of small regular tubercles. The ossicles of the IBr 

 series (united in a syzygial pair) taken together form an element which is oblong, 

 not quite twice as broad as long, with the proximal, distal, and lateral edges everted; 

 the lateral edges are beaded like the distal edge of the radials; the proximal edge is 

 faintly scalloped and bears a prominent median tubercle; the distal edge has the 

 median third of the eversion thickened and standing up vertically as a high transverse 

 ridge; the syzygial line is finely beaded. 



The five arms are 60 mm. long. The first brachial is oblong, about three times as 

 broad as long, with the proximal edge slightly everted and bearing a prominent, though 



