A MONOGRAPH OF THE EXISTING CRIXOIDS 



463 



tinct socket. The cirrus sockets are without any special arrangement on the centro- 

 dorsal; they are somewhat sunken. In three of the four specimens the cirrri number 

 about XL and in the fourth XLV. The longest cirri in each have 55, 47, 43 and 48 

 segments, measuring 27, 23, 23 and 24 mm. in length. The longest cirrus segments 

 are about twice as long as broad. The distal ones are much shorter with a dorsal cari- 

 uation of which the apex is towards the distal end. 



The division series and first brachials have a markedly thickened lateral flange 

 bringing the neighboring ones into contact and the first three brachials also have a 

 flange on the inner side. The synarthrial tubercles on the division series and first 

 pairs of brachials are prominent but not of exaggerated size. 



Figure 19. — Perometra afta A. H. Clark, 

 syntypes, B.M., 1907.7.1.84-6: a, Latero- 

 dorsa! view of centrodorsal; A, proximal 

 part of postradial series of another syntype; 

 c, cirrus tip. 



The specimens are more or less incomplete and some of the division scries are 

 broken so that the e.xact number of arms cannot be ascertained. One specimen cer- 

 tainly has 15 arms and the others all have at least 13. One of the latter could have had 

 20 arms since all those remaining arise from IIBr series and the other IBr series are 

 broken. ^Ul the IIBr series are of two ossicles. The arm length was probably between 

 50 and 65 mm. in all the four specimens. The width at the first syzygy is 1.0-1.1 mm. 

 and the length from the pro.ximal edge of the IBri to the second syzj^gy at 9+10, 

 where no IIBr series intervenes, is about 8.5 mm. 



The pro.ximal pinnules have very slender segments several times as long as wide 

 with prominent hyaline spines at the distal ends of most of them, particularly oa the 

 ventral side. In two of the types Pi and P2 have 14 segments and measure 7.0 mm. 



