570 BULLETIN 82, UNITED STATES NATIONAL MUSEUM. 



larger in the interradial spaces, are very short, about one-fourth or one-fifth as 

 long as the longest, and are indistinctly articulated, with the tips rounded and 

 without claws. 



The disk, with the five ambulacral grooves radiating from the mouth each near 

 the border dividing into two branches which continue onto the corresponding arms, 

 and the anal tube, much larger than at the preceding stage and cylindrical, more 

 or less crenulated at the tip about the anal opening, resembles that of the free-living 

 adult. The five orals have been completely resorbed. 



The IBr, have increased considerably in size and thus appear shorter than 

 in the preceding stage, being about twice as broad as long. The IBr^ are also 

 somewhat broader, being about as broad as long. 



Additional pinnules have developed, five on one side and six on the other of 

 each arm, of which they occupy a little less than the distal half. They have 

 become longer and more developed and are composed of a larger number of seg- 

 ment. The tentacles and sacculi remain as before. 



On the lateral ventral border of each brachial are two rounded flaps, each of 

 which contains as a brace a calcareous rod, as previously described. 



On the outer side of the second brachial a pinnule is now in process of forma- 

 tion which did not exist at any preceding stage; it is still very short, scarcely 

 longer than the width of the brachial, filiform, unarticulated, rounded at the tip, 

 and without tentacles. 



The brachials between the second and the twelfth (in one specimen the tenth) 

 show as yet no trace of pinnules. 



Alreadj' the sygyzies can be distinctly recognized between the third and fourth 

 and ninth and tenth brachials, as in the adults. 



Another specimen 22 mm. long, the crown (with the arms) measuring 6 mm., 

 the column of which is composed of 37 segments, is a little less developed than 

 the last described. The centrodorsal bears only 10 cirri, of which the five largest 

 (the primary cirri, radially situated) are composed of eight segments; the five 

 small cirri are situated immediately above them in the interradial angles. There 

 are as yet only two or three pairs of pinnules on the arms. 



A third indiv-idual, with the column composed of 34 segments, is 20 mm. long, 

 but incomplete, the 10 arms being all more or less broken. On two of the arms 

 there remain only the three lowest brachials. From the distal end of the third 

 brachial (the hypozygal of the first syzygial pair) a new arm has arisen which 

 resembles in a striking manner a young shoot grafted on a tree. It is very short 

 and slender, only 2 mm. long, at the base scarcely half as thick as the stump which 

 bears it, tapering toward the tip, which is curved inward. It is composed of 11 

 or 12 segments and bears no pinnules, though it is already provided with tentacles 

 and with minute sacculi, a pair for each brachial except for the last four or five, 

 on which they are still lacking. The oral pinnule is well developed, consisting of 

 six or seven segments. 



The largest and most developed of all the pentacrinoids was that which Pro- 

 fessor Sars described in 1856. 



