PART 5 A MONOGRAPH OF THE EXISTING CRINOIDS 625 



Sacculi are abundant and conspicuous, regularlj- arranged on the disk, the arms, 

 and the pinnules; in some of the specimens they retained a red color in spirit for a few 

 years. 



Along the pinnule ambulacra of the small and moderate sized specimens there are 

 heavy, well-developed side plates, about three pairs to each segment, but no cover plates. 

 The side plates are finely reticulated. Spicules occiu- in most of the tentacles; they may 

 be smooth rods but are more often very thorny and sometimes branched. 



The color in life of five of the specimens was noted. Four were Ughter in the 

 pro.\dmal than the distal part; the proximal third to half varied from straw j-ellow to 

 bright orange yellow and the distal part from a delicate pink to a deep orange browTi. 

 The fifth specimen was orange yellow. 



Pentacrinoid larvae [from John, 1938].— Fifteen pentacrinoid larvae from Discovery 

 Investigations station 170, off Clarence Island, form a series. Dr. John assumed they 

 belonged to this species since they were taken with adults of it and they are distinct 

 from pentacrinoids of Promachocrinus and Notocrinus, which were also in the same haul. 

 Also the shapes and proportions of the primibranchs and brachials of the oldest ones are 

 similar to those of hordea and the cUstal brachials of the largest larva have a zigzag 

 appearence similar to that found on the middle part of the arms of the adult. The 

 pinnule ambulacra have side plates and the tentacles have numerous spicules similar to 

 those of hordea. 



The youngest specimen is in the cystid or prebrachial stage. The crown is 0.9 mm. 

 long and the column ^vith 26 segments is 3.4 mm. long. The distal part of the column 

 is narrower than the pro.ximal. The first four or five columnals are very short and 

 discoidal, much shorter than wide but increasing in length. The middle columnals 

 are nearly as long as wide, the distal are slightly longer. All are considerably wider in 

 the middle, where they are encircled by a narrow girdle. The terminal plate is thick 

 and rounded. 



The basal cup is considerably wider at the base than the topmost colunmals. 

 The sides are sHghtly convex. The height of the cup is two-thirds of its distal width. 

 The orals form a cup slightly higher than the basals. The lateral edges of the orals are 

 strongly bent outwards to produce a high double ridge along each of the sutures between 

 them. ^Vhen the crown is seen with these ridges in profile, the oral cup has more 

 stronglj^ convex sides than the basal. 



A second specimen has the five radials and the radianal plate present. The crown 

 is about 1 mm. long, the column 5.8 mm., consisting of 28 columnals and a terminal 

 plate. The middle columnals are girdled and slightly longer than broad. The articular 

 faces of the longer columnals are broadly oval, the long axes of the two ends of one 

 columnal being in planes at right angles, while the long a.xes of the two opposing faces 

 of contiguous columnals coincide. The terminal plate is thick and rounded. The base 

 of the basal cup is not wider than the topmost columnals. Its height is equal to that of 

 the oral cup and is considerably less than its distal diameter. The lateral edges of the 

 oral plates are more strongly bent outwards, especially proximally where a furrow lies 

 between those of adjacent plates, than in the prebrachial stage. A small rounded 

 radial plate is present in each of the angles between the basals and the orals. Below 

 and to the left of one of them, which is smaller than the others, is the radianal plate. 

 In this radius the suture between the basals and that between the orals are not in line 

 with one another as they are in other radii. 



