Bd. VI: 8) 
THE CRINOIDEA. 
1 1 
twice as broad as long; the distal edge concave, for the reception of the axillary, 
which is also very broad, */ 3 broader than long. The costals are in apposition laterally, 
at least in their lower part. Both the primibrachs and the lower brachialia are flat- 
tened, with sharp side-edges. The distal edge of the outer brachials is smooth, but 
somewhat thickened, giving the arms a serrate appearance (Figs. 8 a — c). 
Syzygies numerous; the first two constantly on the 3rd and 8th joint (the syzy- 
gial joint counted as one); from the second syzygy on there is mostly two or three 
Fig. 6. Centrodorsal and basal Fig. 7. Cirrus of Iso- 
part of arm of Isometra vivi- metra vivipara. 8 /i. 
para. 8 /i. 
Fig. 8. a. Dorsal view of arm joints from the 
middle of the arm ; b. side view of the same ; 
c. dorsal view of arm joints from distal part 
of the arm of Isometra vivipara. II /i. 
joints between the syzygies, but sometimes only one, or there may be as many as 
four or, rarely, five. 
The oral pinnules (Fig. 9) are ca. 6 — 7 mm long, in grown specimens, P] only 
slightly longer than P. 2 - 3 . They are fairly robust, with 12 — 14 short, smooth joints 
and without a terminal comb. P 3 generally has the ambulacral furrow developed. P 4 
has a slight widening of the 3rd and 4th joint; P 3 is a fully developed genital pinnule. 
The genital pinnules are ca. 9 mm. long, the distal pinnules slightly shorter and some- 
what more slender. 
