PAST 5 A MONOGRAPH OF THE EXISTING CRINOIDS 423 



segments are produced into a rounded keel giving the distal profile a scalloped appear- 

 ance. P 3 is about 25 mm. long with about 50 segments, much stouter than P : and P 2 ; 

 the first two segments are rather broader than long, the remainder about as long as 

 broad; a long gonad lies on the eighth to eighteenth segments, beyond which the pin- 

 nule tapers gradually to a very slender and delicate tip. The dorsal border of the seg- 

 ments of this pinnide is sharply carinate, but the carination rises progressively from the 

 proximal to the distal end so that the dorsal profile presents a serrate appearance quite 

 different from the rounded scallops on the distal profile of P t and P 2 . P 4 is 21 mm. long 

 resembling P 3 , but the segments have finely dentate projecting distal edges, which are 

 especially noticeable dorsally, and the gonad is longer. The following pinnules are 

 similar, gradually decreasing in length and gradually losing the flagellate tip, the seg- 

 ments at the same time becoming more elongated. P 6 is 17 mm. long, with 33 seg- 

 ments, of which the first two are not so long as broad, the third is about as long as broad, 

 and the following are very slightly longer than broad distally, gradually becoming 

 elongated and reaching a length of nearly twice the width terminally. With the gradual 

 disappearance of the gonads, which persist to about the twenty-fifth, the pinnules be- 

 come gradually longer, but remain of the same proportions, the component segments 

 being about as long as broad except in the terminal portion. All the segments of the 

 pinnules have overlapping and finely dentate distal ends, this feature being most marked 

 on the dorsal side. The tenth pinnule is 20 mm. long. The distal pinnules are more 

 slender, about 20 mm. long, with the first segment about twice as broad as long, trapezoi- 

 dal or almost crescentic, the second slightly larger and wedge-shaped, broader than 

 long, the remainder about as long as broad becoming longer than broad terminally. 

 All the segments except the first two have strongly overlapping distal ends. 



The color in alcohol is light brown ; in life it is yellow. 



The preceding description was drawn up from the very fine specimen from Chal- 

 lenger station 151 in the Museum of Comparative Zoology at Cambridge. 



Notes. This species was described by P. H. Carpenter, on the basis of several 

 specimens from Challenger station 151, in the following terms. 



The centrodorsal is hemispherical, thickly covered with cirrus sockets. 



The cirri are LXXX+, 25-35, reaching 35 mm. in length. Several of the seg- 

 ments are longer than broad, and the later ones project slightly beyond the base of 

 their successors. The terminal claw is well developed. 



The radials are concealed except in the angles of the calyx, where they are some- 

 times separated by the ends of the basal rays. The IB^ are quite short and bandlike, 

 very convex in the center and deeply incised. The IBr 2 (axillarics) are usually rather 

 broader than long, subtriangular, with a backward process of variable size in the middle 

 of the base which is sometimes so large as to give the plate an unequally rhombic ap- 

 pearance. 



The 10 arms are about 125 mm. long. They are but slightly tubercular at the base. 

 The first brachial is much incised with a short inner and long outer edge. The brachials 

 after the third syzygy are quite short, triangular, and slightly overlapping. They 

 become slowly quadrate toward the ends of the arms, but always remain broader than 

 long. 



Syzygies occur between brachials 3+4, 9 + 10, and 14 + 15, and then usually at 

 intervals of 4 muscular articulations. 



