i88 DISCOVERY REPORTS 



Isometra hordea n.sp. (Plate V, figs. 7 and 8) 



St. 170. 23. ii. 27. Off Cape Bowles, Clarence Island. 61° 25' 30" S, 53° 46' W. 342 m. Gear 

 DLH. Bottom: rock. Three specimens. 



St. 1873. 13. xi. 36. Off Cape Bowles, Clarence Island. 61° 20-8' S, 54° 042' W. 117 m. 

 Gear DRR. Bottom: rock and stones. One specimen. 



St. 1948. 4. i. 37. East of Clarence Island. 60° 49-4' S, 52° 40' W. 490-610 m. Gear DRR. 

 Four specimens. 



St. 1955. 29. i. 37. North of South Shetland Islands. 61° 35-1' S, 57° 23-3' W. 440-410 m. 

 Gear DRR. Four specimens. 



Description. The larger specimens are moderately big and massive but they appear 

 to be more brittle than the smaller for none of them is complete. The longest remaining 

 arm of the stoutest specimen consists of 42 brachials and measures 45 mm. A much 

 younger and slighter specimen has one complete arm of 93 brachials, 56 mm. long. 



The centrodorsal varies from a low rounded hemisphere to a high rounded cone and 

 it is usually covered with closely crowded cirrus sockets arranged in alternating rows 

 (Fig. 18 b). The dorsal pole may be large or small and either smooth or so beset with 

 tubercles as to be very rough ; or there may be no bare dorsal pole. The ventral edge of 

 the centrodorsal is usually straight but it may be produced into low interradial corners. 



The centrodorsal of the largest most massive specimen (St. 1948) is remarkable. 

 It is a high rounded cone. The only cirri remaining are three or four rows around the 

 ventral edge yet they number 52. Over all the rest of the surface, excepting the small 

 smooth dorsal pole, the cirrus sockets have become quite obliterated by a honey-comb- 

 like growth of stereom. 



Cirri XL-LX ; 25-70. They are of two sizes : there are short apical cirri and peripheral 

 cirri which may be twice as long. In the smaller specimens the apical cirri are of 

 25-35 segments and 10 mm. long, the longer outer cirri are of 38-50 segments and 

 20 mm. or more in length. In the larger specimens the apical cirri may be of up to 

 fifty segments and 16 mm. long; the peripheral cirri are of 50-70 segments and up to 

 40 mm. long. The following is a description of the peripheral cirri of large specimens 

 (Fig. i8«). 



The first four segments are considerably broader than long, the fifth about three- 

 quarters as long as broad. The sixth to about the twelfth are very slightly longer than 

 broad. Four or five beyond the twelfth are as long as broad. Thereafter the segments 

 gradually decrease in length until the distal, which may be twice as broad as long. The 

 long proximal segments are perfectly regular. In the region of the twelfth to fifteenth 

 segments a small swelling appears at the distal end of the dorsal edge. By the twenty- 

 fifth or so it has developed into a long low keel with a straight edge occupying the distal 

 three-quarters of the dorsal edge. On the shorter distal segments the keel is shorter 

 with a curved edge. It becomes weak on the three or four segments before the opposing 

 spine. The opposing spine is usually strong and upstanding, the terminal claw moder- 

 ately strong. There is a sharp diff'erence in colour between the first six to ten segments, 



