A MONOGRAPH OF THE EXISTING CRINOIDS 225 



dorsal; the distal angles of the radials are slightly separated. The IBrj arc short, 

 oblong, about four times as broad as long, not united basally. The IBrz (axillaries) 

 are almost triangular, twice as broad as long, with the lateral edges only half as long 

 as those of the IBri. The synarthrial tubercles are small but prominent. 



The 10 arms are about 80 mm. long and are moderately slender. The first 

 brachials are wedge-shaped, about twice as broad distally as the exterior length, 

 interiorly united for the proximal two-thirds, the interior edges diverging widely in 

 the distal third. The second brachials are of about the same size, irregularly quad- 

 rate. The first syzygial pair (composed of brachials 3+4) is slightly longer interiorly 

 than exteriorly, twice as broad as the interior length. The next four brachials are 

 oblong or slightly wedge-shaped, about three and one-half times as broad as long, 

 those following becoming triangular, about twice as broad as long, and after the middle 

 of the arm wedge-shaped, twice as broad as long, and in the terminal portion wedge- 

 shaped and about as long as broad. From the ninth or tenth onward the brachials 

 have rather prominently overlapping finely spinous distal ends which very gradually 

 die away in the distal third of the arm. Syzygies occur between brachials 3 + 4, 

 again from between brachials 13 + 14 to between brachials 15+16 (with sometimes 

 an extra one between brachials 5 + 6 to 9+10), and distally at intervals of 4-6 (usu- 

 ally 5) muscular articulations. 



Pi is small and weak, from 4.5 to 5 mm. long, composed of 17 segments of which 

 the first is small, irregularly quadrate, the second is wedge-shaped, twice as broad 

 as the proximal (greater) length, the third is half again as broad as long, and those 

 following gradually increase in length to the sLxth which, with the remainder, is about 

 as long as broad. From the third segment onward a dorsal ridge begins to develop 

 along the median external line of the pinnule, after the seventh becoming a high 

 carination. The eighth and following segments bear prominent processes on the 

 distal border on the line of this carination which are triangular in shape, the apex 

 terminal, arising from the whole exterior line of carination, the distal height being 

 equal to about half the \vidth of the segments. P; is 10-12 mm. long, much stouter 

 than Pi and by far the stoutest pinnule on the arm, and very stiff, tapering gradually 

 from the base to a delicate tip; it is composed of 25 segments of which the first two 

 are short and those following gradually increase in length to the fifth which, with 

 the following, is about as long as broad, at the extreme tip becoming somewhat longer. 

 The third and following segments are strongly carinate, the fourth and following 

 bearing on their distal edges along this line of carination sharp and prominent ante- 

 riorly directed spines the bases of which do not involve more than the distal third, 

 or at most the distal half, of the segments; similar, though smaller, spines occur along 

 the inner distal edge of the pinnule. P3 is most like P,, 4 mm. long with 15 segments 

 which become as long as broad on the fifth and from one-third to one-half again as 

 long as broad distally. The second and third segments sometimes develop distal 

 carinate processes, and the third and followmg are obscurely carinate dorsally with 

 overlapping and finely spinous ends which are especially produced along the dorsal 

 rounded-carinate ridge and along the ventral angles. The pinnules following are 

 in general similar, the distal overlap of the segments gradually becoming more uniform 

 in height, after P7 becoming an even finely spinous projection which disappears alto- 



