ISOMETRINAE 185 



Isometra graminea n.sp. (Plate V, figs. 5 and 6) 



St. 190. 24. iii. 27. Bismarck Strait, Palmer Archipelago. 64° 56' S, 65° 35' W. 93-130 m. 

 Gear DLH, NRL. Bottom : ? stones, mud and rocks. A complete female, a specimen with the 

 arms broken off, and parts of the arms of a male and a female. 



130-100 m. Gear DLH, NRL. Bottom: ? stones, mud and rocks. One male. 



St. 1652. 23. i. 36. Ross Sea. 75° 56-2' S, 178° 35-5' W. 567 m. Gear DRR. Bottom: mud. 

 Three males and one female. 



St. 1872. 12. xi. 36. Bransfield Strait. 63° 29-6' S, 54° 03-1' W. 247 m. Gear N 100 H. Bottom: 

 soft mud. One female. 



Description. The male and the female from the Bismarck Strait and the female from 

 the Bransfield Strait are in good condition. The lengths of their arms, from the axillaries, 

 are 40, 40 and 48 mm. respectively. There are larger specimens from the Ross Sea with 

 arms up to 60 mm. long. Notes were made of the colour of some of the specimens when 

 they were captured. The Bransfield Strait specimen was pale straw yellow. Two of the 

 Ross Sea males were "pale yellow brown", one "pale dirty yellow white"; the female 

 was a deep orange brown. The latter is light brown in spirit, whereas the remaining 

 specimens vary from white to yellowish white. The bases of the cirri may be darker in 

 colour and the perisome have a faint greenish tinge. 



The centrodorsal is a rounded cone with its ventral edge produced into very slight 

 interradial corners. There is a bare dorsal pole in all except three of the specimens, one 

 from each of the three stations, in which the centrodorsal is entirely covered with cirri. 

 The cirrus sockets are close-set, arranged in alternating rows which may be slightly 

 irregular. 



Cirri XXVI-XLIII, 28-41 (Fig. 17 a). The lower segments beyond the fourth are 

 longer, except in the specimen from St. 1872, than in /. vivipara and I.flavescens. There 

 is a slight difference between the cirri of the specimens from the Bismarck and Brans- 

 field Straits and those from the Ross Sea. In the latter the first three cirrals and to a 

 lesser extent the fourth are considerably stouter than the succeeding cirrals ; this is not 

 so in the specimens from the other side of the continent. The following description 

 covers those of specimens from both regions. The first two segments are short, the third 

 a little longer. The fourth is longer than broad (except in the specimen from St. 1872). 

 The fifth to about the eighth or ninth are appreciably longer than broad (except in the 

 specimen from St. 1872 in which they are very little longer than broad). The fourth to 

 the eighth or ninth segments may be faintly waisted. The segments beyond decrease in 

 length ; the distal are broader than long and each is produced into a moderate or strong 

 rounded dorsal spine. (The figure is of a short cirrus; in the longer, of more segments, 

 many more of those in the distal part are raised into rounded keel-like dorsal spines.) 



The radials vary in length. In the smaller specimens they are longer in the mid-line 

 than the costals, but in the largest specimens they are much shorter. The distal edge is 

 wider than the proximal and concave. The costals are not in contact with one another; 

 they are incised by the posterior projections of the axillaries which may form slight 



