PART 5 A MONOGRAPH OF THE EXISTING CRINOIDS 393 



the average being 440 meters; but this probably has little significance, as they are so 

 easily overlooked among the fragments of the adults. 



The temperatures range between 1.20 C. and +1-10 C., the average being 

 0.31 C. Though possibly without significance, this may indicate that these ani- 

 mals breed more freely in the colder portions of their range and, where there is a 

 seasonal difference, in the colder season. 



The pentacrinoid from the Dijmphna expedition and the two collected by the 

 Frithiofw Spitzbergen have already been described (Part 2, p. 528). 



The two dredged by the Varna were described by P. H. Carpenter (1887). 

 Though no adults accompanied them there can be no doubt that they represent this 

 species. 



The length of the larger is 35 mm., which is about equally divided between the 

 crown and the column. The latter consists of 29 segments, the last of which is some- 

 what irregular in shape and has rather the appearance of being a root-joint like that 

 at the bottom of the stem in Ehizocrinus and Bathycrinus. The stem as a whole is 

 singularly like that of the young Rhizocrinus. 



Beneath the centrodorsal come three discoidal segments, gradually increasing in 

 thickness. The next is about as high as wide, and those just below gradually increase 

 in height while diminishing slightly in width until they become cylindrical and elon- 

 gated. In the lower part of the stem the width increases again, especially towards 

 the ends of the segments, which assume the characteristic dice-box shape, while the 

 segments immediately above the root-joint, though the stoutest on the whole stem, 

 are distinctly shorter than those above, just as in Ehizocrinus and Bathycrinus. 



The centrodorsal bears 15 cirri, the longest of which reaches 5 mm. in length and 

 consists of about 18 segments with a terminal claw, but no opposing spine, slight 

 indications of which appear on some of the other cirri. 



The radials are partly overgrown by the centrodorsal so that but little of their 

 dorsal surface is visible, though they extend upwards in the interradial angles of the 

 calyx at the sides of the IBr! ; these are relatively long, transversely oblong, and con- 

 siderably incised to receive the posterior process from the rhombic axillaries. 



There are over 30 elongated brachials, the second with a slender pinnule 3 mm. 

 long and consisting of about 15 segments; the P a are mere stumps of less than half a 

 dozen segments, but the next four pinnules gradually increase in size. Beyond this 

 point the arms present a certain amount of variation. Two or three brachials are 

 altogether devoid of pinnules on some arms, and the first long pinnule, consisting of 

 12 slightly elongated segments, appears on the tenth or eleventh brachial; while on 

 other arms these brachials bear pinnule stumps but smaller ones than those on the 

 brachials nearer the axillaries. 



The two basal segments of the outer and longer pinnules are shorter than their 

 successors, trapezoidal in shape, and in contact by their longer ends, thus showing 

 traces of the peculiarity which is so especially marked in Heliometra glacialis. 



In the smaller pentacrinoid the column measures 18 mm. and the crown 14 mm. 

 The column consists of 18 segments, most of which are cylindrical; but instead of three 

 discoidal segments immediately beneath the centrodorsal there is only one. This is 

 somewhat hexagonal in outline, being wider a little above its equator than at either 

 end, while the segment below it, although longer than wide, exhibits a similar expan- 

 sion for some little way down from its upper end. 



