A MONOGRAPH OF THE EXISTING CRINOIDS 653 



Carpenter says elsewhere that this specimen is about the same size as the type 

 series of polymorpha (from Bohol), so that the arm length would be from 100 to 110 

 mm. 



The 10 IIBr series and the 9 IIIBr series present are all 4 (3 + 4). 



Around the margin of the centrodorsal there are only 10 cirrus sockets, 2 on 

 each of its sides, which are placed close to the interradial angles. 9 The number of 

 segments in each cirrus is 11 or 12. The width of the 2 basal segments somewhat 

 exceeds their length; in the third the length and width are nearly equal, and in the 

 fourth and fifth, which are the longest, the proportion between them is about 4 to 3. 

 The sixth segment is slightly shorter than the fourth, and from this point to the end 

 of the > cirrus the length of the segments gradually decreases, while at the same time 

 they exhibit a slight degree of lateral compression. The dorsal spine, the first in- 

 dication of which is seen in the fifth and sixth segments, becomes very marked indeed 

 toward the end of the cirrus, and develops on the penultimate segment into a stout 

 opposing spine. 



The position of the first 3 brachial s3 T zygies varies as follows: Between brachials 

 3 + 4, 5 + 6, 7 + 8 (once); brachials 3+4, 11 + 12, 16 + 17 (23 times); brachials 3 + 4, 

 11 + 12, 18 + 19 (once); 3 + 4 11 + 12, 21+22 (once); 3 + 4, 12 + 13, 17 + 18 (once); 

 3+4, 13 + 14, 18+19 (once). 



The number of muscular articulations in the first intersyzygial interval varies as 

 follows; 1 (once); 7 (25 times); 8 (once); 9 (once). 



The number of muscular articulations in the second intersyzygial interval varies 

 as follows: 1 (once); 4 (25 times); 6 (once); 9 (once). 



In the distal intersyzygial intervals the tendency is toward an increase in the 

 number of muscular articulations over the normal, 5 occurring much more commonly 

 than 3. 



As variety 1 of Actinometra polymorpha Carpenter described a specimen from 

 Ubay in the following terms: 



The cirri are XXV, 13-15. The spines on the dorsal surface of the distal seg- 

 ments are not very distinct, but the segments are laterally compressed. 



The IBr[ are completely united. 



The 20 arms are 52.5 mm. long. 



The distal intersyzygial interval varies from 2 to 11 muscular articulations, but 

 is usually 4. 



Combs occur uninterruptedly as far as the sixth brachial pinnules, and then at 

 intervals to about the twentieth brachial, but no further. The basal pinnules of the 

 arms have a faint dorsal keel, and the distal ends of their segments are rather wider 

 than the proximal. 



The disk is about 8 mm. in diameter. 



Carpenter noted that the cirri of this variety present some slight differences 

 from those of the type series of polymorpha. Not only is the number of segments 

 greater, but these latter also differ considerably in their relative proportions. While 

 in the typical form the fifth and sixth segments are the longest, in this variety there 

 is less difference between them and the fourth and seventh in this respect. The lateral 



'Vol. 1, pt. 1, flg. 176, p. 231. 



