A MONOGRAPH OF THE EXISTING CRINOIDS 29 



deeply concave. The cirrus sockets are arranged in 2 closely crowded more or less 

 alternating rows. 



The cirri are XX, 30-32, from 20 mm. to 25 mm. long, and stout. The cirrus 

 segments are remarkably uniform, all about twice as broad as long, with very promi- 

 nent distal dorsal ends which after the tenth become a pair of dorsal tubercles. The 

 dorsal profile of the cirri is strongly serrate. 



The radials are barely visible; their anterolateral angles are slightly separated. 

 The IBri are oblong, short, about 3 tunes as broad as long, rounded dorsally and widely 

 separated laterally with a strong rounded triangular ventrolateral process on either 

 side supporting the visceral mass. The IBr 2 (axillaiies) are broadly pentagonal, rather 

 over twice as broad as long, with a somewhat larger ventrolateral process on either 

 side than the IBrj. The IIBr and IIIBr series are 2, the latter developed only on the 

 outer side of the postradial series. All of the elements of the division series and the 

 first 2 brachials bear stout ventrolateral processes. 



The 30 arms are 140 mm. in length. The first 8 brachials are oblong, about 

 twice as broad as long, those following becoming slightly wedge-shaped, about twice 

 as broad as long, then gradually less and less wedge-shaped and practically oblong 

 again and about twice as broad as long in the distal half of the arms. Except for the 

 proximal discoidal series the brachials have everted and finely spinous distal ends 

 giving the arms a characteristic rough feeling, much as in Catoptometra. 



Syzygies occur between brachials 3 + 4, again from between brachials 14+15 to 

 between brachials 42+43 (usually in the vicinity of the thirtieth), and distally at 

 intervals of from 6 to 12 (usually 7-9) muscular articulations. 



P! is very slender, 12 mm. long with 28 segments of which the first 2 are about 

 twice as broad as long, the following increasing in length to the fifth, which is about 

 as long as broad, then slightly longer than broad, and about half again as long as 

 broad distally. P 2 is 15 mm. long, very stout and stiff, with 20-23 segments the first 

 2 nearly twice as broad as long, the third about as long as broad, the remainder 

 slightly longer than broad; the fourth or fifth and following have the distal ends 

 dorsally and laterally everted and spinous, though ventrally they are unmodified. 

 P 3 is smooth, 6 mm. long, or one-half the length of PI, small but rather stiff, tapering 

 evenly from the base to a slender tip, with 13 segments of which the distal are about 

 half again as long as broad. P 4 is similar, but only 5 mm. long. The following pinnules 

 are similar, but very gradually increase in length. The distal pinnules are 10 mm. long 

 with 20 or 21 segments of which the first is nearly twice as broad as long, the second is 

 trapezoidal and nearly as long as its greater (proximal) width, and the remainder are 

 about half again as long as broad. All of the pinnules are somewhat stiffened. 



The color in alcohol is reddish brown with the enlarged P 2 lighter, or yellow, the 

 remaining pinnules nearly black in then- proximal, white in their distal half; or light 

 blue-gray with numerous small reddish-brown spots; the cirri are reddish brown. 



Notes. The preceding description is based upon the type specimen of Himero- 

 metra unicornis from Albatross station 5160. 



As described by Dr. Gisl6n, the specimen from the Bonin Islands has the centro- 

 dorsal thick discoidal, 1.5 mm. in height, with raised margins about the bare dorsal 

 pole, which is 2 mm. in diameter. The cirri are arranged in two marginal rows. 



