A MONOGRAPH OF THE EXISTING CRINOIDS 147 



The IBri are three times as broad as long, and bear a very slight median carination. 

 The IBr 2 (axillaries) are one-third again as broad as long. 



In the third specimen from Mortensen's station 9 the cirri are XVI, 16-21, from 

 4 to 8 mm. long, and are arranged in a single row. The segments are about as long as 

 broad, or shorter. A transverse bi- or tri-dentate ridge arises on the fifth or eighth 

 segment, later transforming into a stout dorsal spine. The 10 arms are 50 mm. long. 

 The distal edge of the radials is even with the rim of the centrodorsal. The inter- 

 syzygial interval is 4-6 muscular articulations. PI is 3.5 mm. long with 12 segments. 

 P 2 is 6.0 mm. long with 14 segments. P 3 is 4.2 mm. long with 11 segments. 



From Dr. Th. Mortensen's station 10 Dr. Gisldn recorded 172 specimens. In 

 the 152 specimens examined the number of arms was as follows. Thirty-seven have 

 10 arms, which are 33, 37, 37, 37, 38, 38, 40, 42, and 43 mm. long in the 9 specimens 

 hi which they were measured; 31 have 11 arms, which in 3 are 30, 35, and 45 mm. 

 long; 39 specimens have 12 arms, which in those measured are 36, 40, 40, 40, 45, and 

 50 mm. long; 23 have 13 arms, which in 3 are 27, 42, and 42 mm. long; 9 have 14 

 arms, which in 3 are 33, 35, and 40 mm. long; 4 have 15 arms which in 2 are 30 and 47 

 mm. long; 5 have 16 arms which in one are 31 mm. long; 3 have 17 arms which in one 

 are 37 mm. long; and one has 18 arms 40 mm. long. GislSn said that in no case do 

 IIIBr series occur. The IIBr series are 2, except in three cases (see p. 157). The 

 occurrence of IIBr series shows three different types; a IBr series may bear two IIBr 

 series, or a single IIBr series which may be developed either on the left or the right 

 side. Gisle"n said that it is not possible to discover a definite preponderance of any 

 one of these three types. In 224 cases investigated, 49 belonged to type 1, with two 

 IIBr series on a IBr axillary; 79 belonged to type 2, with a single IIBr series on the 

 left face of a IBr axillary; and 96 belonged to type 3, with a single IIBr series on the 

 right face of a IBr axillary. Dr. Gisl6n noted that, curiously enough, the small 

 specimens usually have type 2, while on the contrary the large specimens show type 3. 

 In a specimen with only one IIBr series type 3 is more usual than type 2 (17 cases as 

 against 12). When type 1 occurs and there are division series also on adjacent post- 

 radial series, it is usually the postradial series nearest to type 1 that possesses them. 



In one specimen from Mortensen's station 10 the cirri are XXV, 24, about 11 

 mm. long, arranged in two rows on the centrodorsal. The 10 arms are 40 mm. long. 

 The intersyzygial interval in 3-5 muscular articulations. P! is 3.2 mm. long with 12 

 segments. P 2 is 4.8 mm. long with 15 segments. P 3 is 3.1 mm. long with 12 segments. 

 The disk is 3.5 mm. in diameter. The color is yellowish with solitary small violet 



spots. 



In another specimen from Mortensen's station 10 there are XXV cirri. The 

 15 arms are 47 mm. long. On one postradial series the IBr axillary bears a IIBr 

 series on the left, and on the right an undivided arm with brachials 3 and 4, as well as 

 1 and 2, united by synarthry, and a pinnule on the fourth brachial. PI is 3.5 mm. 

 long with 13 segments. P 2 is 5.7 mm. long with 16 segments of which the distal have, 

 small distal tubercles, as in the first specimen described from Bock's station 13. 

 P 3 is 3.5 mm. long with 12-13 segments. The distal pinnules are 4.7 mm. long with 17 

 segments. The disk has been thrown off. The color is yellowish. 



In a third specimen from Mortensen's station 10 the cirri are XXIII, 22, 9 mm. 

 long. There is a weak dorsal thickening on the middle segments. The 17 arms 



