A MONOGRAPH OF THE EXISTING CRINOIDS 221 



Another specimen has the arms 60 mm. long and the cirri XVI, 15-22. P : is 4.5 

 mm. long with 12 segments of which the last 4 or 5 have the distal angles produced 

 slightly beyond the bases of those succeeding. P 2 is 6.5 mm. long with 14 or 15 seg- 

 ments which beyond the fourth have the distal border slightly prominent and very 

 finely spinous, this feature being most prominent at the prismatic angles; the third 

 segment is about as long as broad, and the outermost segments are not quite twice as 

 long as broad. P 3 resembles P 2 , and is of about the same size, or very slightly smaller; 

 it is composed of 13 segments. P 4 is 5 mm. long with 12 segments and resembles P 3 . 

 P 6 is 3.5 mm. long with 12 segments, and is more slender and more flexible than P 4 . 



In one of the remaining specimens P 2 is very stout, while in two others it is slender 

 with elongated segments. The arms of two of these are 45 and about 60 mm. long. 



In one of the specimens from off Jolo in about 46 meters the arms are 40 mm. long. 

 This is a very slender individual. P 2 is 5 mm. long with 11 segments of which the first 

 is half again as broad as long, the second is as long as, or slightly longer than, broad, 

 the third is three times as long as the median width, and the remainder are between 

 three and four times as long as the median width. The third and following segments 

 are slightly constricted centrally. The distal edges of the third and following seg- 

 ments are finely spinous. Pa resembles P 2 , but is much smaller. 



Three other specimens from the same locality and depth have the arms 40, 45, and 

 50 mm. long. 



The largest of the six specimens from Sibutu has the arms 55 mm. long. In these 

 specimens P a is usually absent, but in some it is present on some arms. P 2 is stout 

 with strongly to very strongly developed processes on the segments. On one of the 

 specimens P 3 resembles P 2 on one of the arms. 



Carpenter described the type specimen of Antedon serripinna from Andai, New 

 Guinea, as follows: The centrodorsal is discoidal, bearing marginal cirri. The cirri 

 are about XII, 18. The segments are thick, and none of them are longer than broad. 

 The penultimate bears a blunt spine. The radials are scarcely visible even at the 

 angles of the calyx. The IBr t are nearly oblong and are not united laterally. The 

 IBr 2 (axillaries) are less than twice as long as the IBn and are almost triangular with 

 wide distal angles and slight backward projections from the middle of their bases. 

 The 10 arms are about 30 mm. long. The first brachials are almost rhomboidal and 

 are closely united laterally. The second brachials are distinctly shorter and more 

 wedge-shaped. The first syzygial pair (composed of brachials 3 + 4) is transversely 

 oblong or nearly square. The next few brachials are short and oblong, and those 

 following are longer and sharply wedge-shaped, gradually becoming blunter toward 

 the arm ends. The first syzygy is between brachials 3 + 4 and the next is usually 

 from between brachials 12 + 13 to between brachials 16 + 17, the distal intersyzygial 

 interval is usually 4 or 5 muscular articulations. The stoutest pinnules are P 2 and P b . 

 These consist of about 15 segments all but the uppermost of which are short, broad, 

 and thick with their distal edges projecting beyond the base of the next segment so as 

 to give the pinnule a serrated outline. PI and P 2 are slightly longer than P a and P b . 

 Those immediately following are shorter and are composed of a few elongated seg- 

 ments, after which the length of the pinnules gradually increases, though it never 

 much exceeds that of the large lower pinnules. The disk is barely 5 mm. in diameter 



