656 BULLETIN 82, UNITED STATES NATIONAL MUSEUM VOLUME 1 



same early stage of development, having no skeletal plates within them and no bands 

 of cilia around them. 



Remarks [by A.M.C.]. Dr. Dilwyn John has described a subspecies antarctica of 

 P. longipinna from off South Georgia and Clarence Island. It is distinguished from 

 the types of longipinna by the smaller number of cirrus segments, the more irregular 

 arrangement of the cirrus sockets and the relatively shorter pinnule segments. 



Locality. Challenger station 320; off the mouth of the river Plate (lat. 3717' S., 

 long. 5352' W.); 1097 meters; temperature 2.89 C.; green sand; February 14, 1876 

 [P. H. Carpenter, 1888; John, 1938J (3, B.M.). 



PHRIXOMETRA LONGIPINNA ANTARCTICA John* 



Phrixometra longipinna var. antarctica JOHN, Discovery Reports, vol. 18, 1938, p. 123 (listed), p. 126 

 (in distribution table), p. 127 (brood pouches alongside and distal to the ovaries), p. 129 (dis- 

 tribution), p. 132 (in key), pp. 164-169 (stations; description of females and male differences); 

 text-fig. 10, p. 166; pi. 4, figs. 5, 6. 



Diagnostic features. The cirri are about XLV, 17-19; the first genital pinnule, P 2 

 or P 3 , is about half as long as the preceding one. 



Description. Female from Discovery Investigations station 156, now designated 

 as lectotype. 



The centrodorsal is a rounded cone with the dorsal pole large and rough. The 

 cirrus sockets are closely crowded and arranged in indistinct columns more irregular 

 than those of the types of longipinna. The ventral edge of the centrodorsal is produced 

 into interradial corners. 



Cirri about XLV, 17-19. The second segment is as long as broad, the third nearly 

 twice as long as broad, a little constricted in the middle and considerably wider at the 

 distal end than proximally. The fourth to sixth segments are the longest, up to two 

 and a half times as long as broad; like the third they are constricted in the middle and 

 expanded at the distal end. The following segments are progressively shorter but all 

 are longer than broad. In addition they are laterally compressed so that the distal 

 part of the cirrus is considerably wider than the median part. The opposing spine is 

 strong, standing out at right angles to the penultimate segment. The terminal claw is 

 also strong and is curved. 



The radial is short. The IBri is much longer; it is narrowed distally and is deeply 

 incised by the posterior projection of the axillary, IBr 2 . The latter is about as long as 

 broad; the proximal edges are straight, the distal deeply concave. The adjacent IBr 

 series are not in lateral contact. 



On three of the arms one or more of the proximal syzygies are irregular in position, 

 otherwise they are between the usual brachials. 



The 10 arms were probably about 25 to 30 mm. long when complete. The longest 

 remaining one has 35 brachials and is 20 mm. long. 



The first brachials are short and incised by the second ones, which are slightly 

 longer than broad and roughly triangular with the inner and distal edges concave, the 

 outer convex. The brachials between the first two syzygies are roughly rectangular, 

 those between the second and third syzygies are longer on one side than on the other 

 and a little longer than broad. The distal brachials are more elongate and rectangular. 



After the first four brachials, which are smooth, the distal edges become slightly 

 raised and produced into spines which become conspicuous on the outer part of the arm. 



* See also Addenda (p. 837) under 1963. 



