642 BULLETIN 82, UNITED STATES NATIONAL MUSEUM VOLUME 1 



The columimls now incrciise in length, and their number, 18, can be determined. 

 They are still quite short, with the central annulus projecting strongly, which gives 

 the column a seirate appearance. Now only the youngest columnals lie within the 

 basal ring. 



Contemporaneously with the lengthening of the stalk, the orals begin to acqube 

 prominent lateral borders. 



In the next stage the characters of the orals are much more marked, the upturned 

 lateral borders being broad and thickened; generally speaking, the cah-x plates are un- 

 usually thick and massive, and are finely tuberculated. Along the lower edge of the 

 orals, a zone of growth is very distinct, indicated by the linear disposition of the holes, 

 which are very small. The radials have appeared, and also the radianal, which is 

 slightly larger than the corresponding radial, and thus has been formed prior to the 

 latter. The columnals have lengthened considerably, especially the lower ones, and 

 are now more rounded in outline, the median annulus being much less prominent. 

 There are 2 1 of them. 



In the following stage the radials have increased considerably, and, hke the orals 

 and basals, show a distinct zone of growth. The IBr, have formed and have assumed 

 the shape of an elongate scale. Within the tentacles elongate spicules have developed. 

 The radianal has already been exceeded by the corresponding radial ; it covers the corner 

 of the latter and of the adjacent oral. It is of the same dense structure as the other 

 calj'x plates. The columnals are about to assume their final form, but the median 

 annulus still projects slightly. There are 24 colmnnals, of which the short proximal 

 are somewhat broader than the others. The terminal stem plate is shghtly lobed. 



In the most advanced stage found, the first pinnule has appeared, on the twelfth 

 brachial. The first whorl of cirri, radial in position, has been formed. The radials 

 and the IBr, have become much broader, and are about to assume their final shape. 

 The orals, l3^ng in the middle of the disk which has increased considerablj^ in size, are 

 widely separated from the basals. The radianal remains small and is no longer in 

 contact with the adjoining radial and oral. Along the arms some branching spicules 

 are seen, representing the side and covering plates. The stem contains 24 columnals, 

 which are slightly thickened at the ends. The upper half of the stem is stouter and 

 more robust than the lower half. The 4 topmost columnals are quite short and increase 

 in width to the centrodorsal, which is the broadest. 



In another specimen there are 3 pinnules on each arm, and a second whorl of cirri 

 is beginning to develop alternating with the first. The cirri in the first whorl are now 

 fully formed, with 14 segments and a terminal claw. 



Localities. — Antarctic (Swedish South Polar Expedition) station 5; southeast of 

 Seymour Island, in the Graham Land region, south of Cape Horn (lat. 64°20' S., long. 

 56°38' W.); 150 meters. [Mortensen, 1918] (1, CM.). 



Antarctic station 5a; same locality and depth [Mortensen, 1918]. 



Antarctic station 59; Burdwood Bank, south of the Falkland Islands (lat. 53°41' S., 

 long. 61°10' W.); 137-150 meters; bottom temperature 3.20° C. [Andersson, 1904, 

 1908; Mortensen, 1918] (4, S.M.). 



Antarctic station 58; Burdwood Bank (lat. 52°29' S., long. 60°36' W.) ; 197 meters; 

 bottom temperature 4.30° C. [Mortensen, 1918] (1, S.M.). Restricted type locaUty. 



Antarctic station 2; off the Rio de la Plata (lat. 37°50' S., long. 56°11' W.); 

 100 meters [Mortensen, 1918]. 



