PART 5 A MONOGRAPH OF THE EXISTING CRINOIDS 589 



Though this species is so excessively brittle that data gathered from museum 

 specimens must be used with great care, it is probably true that it reaches a larger size 

 in the western and southern portions of its range than in the northeastern, since it is 

 also more abundant in the same area. 



[NOTE BY A.M.C.] Blacker (1957) has commented on the fact that the Ernest Holt 

 failed to take this species in the Bear Island-Spitzbergen area during her many cruises 

 since 1949. He concluded from this that there has been a limitation of the range of 

 this species among others due to the increase in temperature in this area. 



Occurrence of the pentacrinoids.The pentacrinoid young of this species have been 

 found at the following localities: Danmark station 99, off northeastern Greenland, 304 

 meters; Kangerdlugsuak, southeastern Greenland, 175 meters; Jan Mayen, 180 to 

 400 meters; east of Jan Mayen (lat. 7205' N., long. 036' W.), 175 meters; Ingolj 

 station 119, northeast of Iceland, 1846 meters; Ingolj station 59, east of Iceland, 567 

 meters; and in the "cold area" of the Faroe Channel. A detailed description of the 

 pentacrinoids was given in part 2, p. 559. Heding (1935) has added some remarks 

 and a figure of a pentacrinoid from Kangerdlugsuak. The specimens from that locality 

 were not fixed to crinoids but to polyzoa. They were conspicuous for their size, the 

 smallest one measuring 48 mm., while the largest is a third again as large. The stem 

 of the smallest consists of 57 to 58 columnals, those nearest to the calyx being discoidal. 

 Several of the columnals towards the calyx are formed of a stem syzygy. The end of 

 the distal columnal extends to a rather large digitate mass, which expands over the 

 surface of the object of attachment. The calyx is well-developed with a few cirri, 

 which are broken. The arms are also broken but some pinnules were developed. A 

 columnar fragment found on a polyzoan shows that this species may develop processes 

 to assist in attachment from the columnals above the terminal ones. 



Occurrence compared with that of Heliometra glacialis. -Whereas Poliometra prolixa 

 does not occur about southern Greenland, farther west than Grinnell Land, or farther 

 east than Wilczek Land, Heliometra glacialis ranges southward to Massachusetts, 

 westward to Hudson Bay, and eastward to Wrangel Island, near Bering Strait, while 

 it is also found slightly farther to the southward about Iceland and on the Finmark 

 coast. 



There are no less than 101 records for Heliometra glacialis beyond the area from 

 which Poliometra prolixa is known, and the fact that within this area there are 228 

 records for Heliometra glacialis as against only 87 for Poliometra prolixa would seem to 

 show the more uniform distribution of the former over the sea floor even when allow- 

 ance is made for the lesser size, less striking color, and greater brittleness of the latter, 

 which render it much less attractive as an object for preservation. 



The bathymetric range of Poliometra prolixa is 596 meters greater than that of 

 Heliometra glacialis, but on the other hand the thermal range is about 4 less. 



The average depth of the habitat of Poliometra prolixa is 311 meters deeper than 

 that of Heliometra glacialis, and the average temperature 0.87 less. 



The average depth of the occurrence in maximum abundance for Poliometra 

 prolixa is 473 meters deeper than for Heliometra glacialis, and the average temperature 

 is 0.51 less. Whereas Poliometra prolixa has not been found in great quantities at a 

 lesser depth than 280 meters, Heliometra glacialis occurs very abundantly in 46 meters. 



History. This species was first taken by the Austrian steamer Tegetthof south 

 of Wilczek Land in 1873. Two years later it was dredged by the Discorcry in Dis- 



