242 BULLETIN 82, UNITED STATES NATIONAL MUSEUM 



P 2 is half again as long as PI and proportionately stouter with 21 or 22 segments of which 

 the longest are only slightly longer than broad. P 3 and the following pinnules are 

 shorter and more slender than Pj. P 3 has 14 or 15 segments. The distal pinnules are 

 long and slender with from 32 to 36 segments. 



Notes. Under the name Antedon serripinna Dr. Clemens Hartlaub described 

 9 specimens from the Tonga Islands in the following terms: 



The centrodorsal is flat discoidal with a smooth, sometimes slightly concave, 

 dorsal pole. The cirri are arranged in a single marginal row. The cirri are about XX, 

 about 20, about 11 mm. long. The segments are approximately equal with a broad 

 dorsal surface, and almost all of them are broader than long. In the proximal half 

 of the cirri the distal ends of the segments overlap the bases of those succeeding. 

 The dorsal side of the distal segments bears a very slight transverse ridge. The 

 opposing spine is sometimes only feebly developed. The radials are only slightly 

 visible in the interradial angles of the calyx. The IBr, are very short, laterally free 

 or in loose contact. The IBr 2 (axillaries) are short, pentagonal or almost triangular. 

 A small synarthrial tubercle is developed on the articulation between the elements 

 of the IBr series. 



The 10 arms, which are up to 60 mm. in length, have an uneven dorsal surface. 

 The first brachials are rather short, and are laterally united interiorly. The second 

 are of about the same size, and are somewhat longer exteriorly than interiorly. The 

 first syzygial pair (composed of brachials 3+4) is larger than the second brachials, 

 and is longer ulteriorly than exteriorly. Following the first syzygial parr there are 

 a few short discoidal brachials, and then a long row of rather short triangular ones. 

 The triangular brachials have markedly produced distal ends that overlap on alter- 

 nate sides the succeeding brachials. Also, the articulation between the first two 

 brachials is not smooth. The brachials remain wedge-shaped almost to the arm 

 tips; here they become blunter, and finally more oblong. There is a small synarthrial 

 tubercle on the union between the first two brachials. The first syzygy is between 

 brachials 3+4. The position of the second is individually somewhat variable; it is 

 commonly about brachials 9 + 10, but may be between brachials 13 + 14. The distal 

 intersyzygial interval in some specimens is 3 or 4, but in others 6 or 7 muscular 

 articulations. 



In the proximal portion of the arms the distal ends of the pinnule segments 

 tend to overlap the basis of the segments succeeding. On the pinnules of the first 

 pan- (Pi and P a ) this is only slightly evident. P] is about 4 mm. long. P a is markedly 

 smaller. The longest and stoutest pinnules are P 2 and P b . P 2 measures 6 mm. in 

 length and is composed of about 14 rather short segments. P 3 and P 4 are markedly 

 smaller than P 2 , and are of about the same length. The pinnules immediately suc- 

 ceeding are the shortest. The following pinnules reach a length of 7 mm. The 

 basal segments of the proximal pinnules are rather strongly broadened, and in the 

 other pinnules in the earlier portion of the arms also the second and third segments 

 tend to be especially large. The disk is not preserved. Sacculi are closely set on the 

 pinnules. 



The color in alcohol is light brown with dark bands and spots on the brachial 

 articulations. The centrodorsal and the cirri are uniform light brown. 



Hartlaub said that these specimens differ from the type specimen from Andai, 



