PART 5 A MONOGRAPH OF THE EXISTING CRINOIDS 25 



The radials are prominent, strongly concave anteriorly, and somewhat produced 

 in the interradial angles. The IBpi are oblong, twice as broad as long, with the lateral 

 edges straight. The IBr2 (axillaries) are broadly pentagonal, about half again as long 

 as the IBri, with the distal angle rounded and the lateral edges straight, continuing 

 distally the lateral edges of the IBri. In hfe the IBr series are probably Just in apposi- 

 tion, but the component segments are sharp edged and not laterally flattened. 



The 10 arms are about 20 mm. long. The brachials are mostly wedge-shaped 

 and about as long as broad, rounded dorsally and with no trace of carination; the first 

 two brachials are sHghtly larger than the others. 



Syzygies occur between brachials 3+4, 7 + 8, and usually 11 + 12 (sometimes 9+10 

 or 10 + 11), and distally at intervals of usually 2 muscidar articulations, though fre- 

 quentty one syzygial pair immediately follows another. 



P], P2, and P3 are small and weak, very short, equal in length to a syzygial pair and 

 one other brachial, composed of five segments of which the first is about as long as 

 broad and the remainder are rather longer than broad. These pinnules taper gradually 

 from the base to the tip. Pi and the pinnules following are about half again as long and 

 much stouter, composed of about seven segments of which the first two are short and 

 the remainder are rather longer than broad; the first three segments are stout, the 

 pinnule tapering rather sharply from that point to the tip. The segments are rounded 

 dorsallj', but are rather sharply convex. 



The sacculi are large and closely set along the ambulacra. 



The color is light purple, the perisome deep purple. 



There is no trace of an ambulacral skeleton. 



The preceding description was drawn up from the type specimens which Dr. H. L. 

 Clark courteously permitted me to study during a visit to Cambridge. 



In two syntypes, immatm"e but with nmnerous pentacrinoids, mostly j'oung, the 

 cirri have 32 or 33 segments the longest of which are not quite so long as broad; Pi has 

 7 segments. 



Young individuals. — Dr. H. L. Clark said that in the earliest free-swimming stage 

 he found the arms are about 7 mm. long and have about 9 pinnules on each side. 

 Distinct syzygies are present between brachials 3+4, 7 + 8, and 11 + 12, but in the re- 

 maining 16 to 18 brachials syzygies have not as yet developed. Pi has only 4 or 5 seg- 

 ments, but is somewhat stouter than the pinmdes succeeding. There are VI cirri, 

 each with about 30 segments. The basals can no longer be distinguished, and the orals 

 are reduced to a few large irregular fragments in each interradius of the disk. 



Notes. — Dr. H. L. Clark originally described this species under the name of 

 Himerometra paedophora in the following terms. 



The centrodorsal is small and discoidal with the cirrus sockets arranged in a single 

 row. 



The cirri are X-XV, 25-35 (usually 28-30). The fu-st four basal segments are 

 broader than long, but the segments succeeding are about as long as broad. The seg- 

 ments are all smooth, or nearly so, until near the tip of the cirri, where a slight longi- 

 tudinal keel is barely developed on the dorsal side of each segment. In some cases 

 this keel gives rise to a slight spine, but even on the penultimate segment no conspicuous 

 spine is found. The terminal claw is short and blunt. 



The radials are barely visible. The elements of the IBr series are not at all swollen 

 or peculiar in any way. The IBr, are much broader than long, narrower prox-imally 



