KUNGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 59- NIO 4. 7 



Arms 10. Very different in length. The long adoral ones always with ambula- 

 cral furrows, more slender, 65 — 95 mm. The aboral ones 2 /3 of their length, 35— 

 45 mm. 



The latter ones are thicker and more clumsily formed, usually without ambulacral 

 furrows. The proximal segments are also strongly enlarged and extended from about 

 the 8 th to the 30 th segment. This condition is no doubt connected with the special 

 way in which the Comasterids move, described by H. L. Clark in 1915. In their 

 creeping movements they make use of the posterior arms as levers and obviously 

 on account of this the strained surfaces of the segments that support the flexor 

 muscles have become somewhat enlarged. 



The R. with dorsal knöt proximally in the median line, in most cases con- 

 cealed by Cd. I Br 1 and 2 united by syzygy. Br 1 and 2 with the same mode of 

 articulation. The breadth of I Br 1 about 5 ti mes its length, it is narrow, bandlike, 

 laterally united. I Br 2 pentagonal, the axillar angle greater than 90°, often with a 

 shallow, dorsal notch at the point. The first Br:s inside more or less brazed in 

 couples. 



Second Br. -syzygy between segment 3 and 4, third at about 10 th , fonrth at 

 about 16 th segment, after that usually with an interval of 5 segments. About the 

 first 7 Br. -segments discoidal, then dorso-distally tongue-like prolonged, alternately 

 on the right and the left side (ef. A. H. Clark op. cit. 26, fig. on p. 97. It is to 

 be observed that the regular alternation of right and lett prominences that I have 

 found in my specimens is not visible in his drawing). Along the median line at the 

 dorsal side of the arm rims a weakly developed crista, usually light coloured. 



The mouth is admarginal, situated in a raclius. Anus subcentral. Disk with 

 limegranules more or less developed. 



P x 9 — 11 mm. The number of the segments varies between 30— >45. The 10 

 — 30 outermost ones with combs. The typical pectinata has 25 — 30 segments pro- 

 vided with combs, the pupurea-iovm OIU y 10—15. The basal segments 2 and 3 at 

 P, and in a still higher degree at P 2 enlarged and outwardly (i. e. on the side that 

 is directed towards the top of the arm) carinate (ef. Chall. Exp. Vol. 26, Tab. 53, 

 fig. 18—20). Po a little shorter with > 30 segments and 10—25 teeth. The pupurea- 

 form with the combs less developed. From P :j the segments are shorter, coarser, 

 without combs, 15 — 20-jointed, 4—5 mm. The 4 outermost segments have the dorsal 

 spines more accentuated, strengthened by hooks, one or two rows on each segment, 

 with about 3 hooks in every row (ef. A. H. Clark op. cit. 42, fig. 52). On the 

 pinnules with low ordinal there are still rudimentary combs shaped like small ven- 

 tro-distal prominences. 



Johannes Muller distinguished in his ti me Comatula purpurea and pectinata 

 as two species. Carpenter, in his work on the Crinoids of the Challenger Expedition, 

 levelled this species under C. pectinata and they were regarded as one species till 

 A. H. Clark 1910 (op. cit. 26) once more began to advocate their differentiation. C. 

 pectinata was supposed to have a more or less connected row of C: i, purpurea having 

 them concentrated in small interradial groups. 



