H3 



P enlarged lower pinnules with comparatively short segments 

 vvhich have broad longitudinal flange-like processes on the 

 outer part of the prismatic ridges Oligometra 



Petasometra A. H. Clark. 



A. H. Clark. Smithsonian Miscellaneous Collections, vol. 60, 191 2, N n 10, p. 25. 

 Die Fauna Südwest-Australiens, vol. 4, 1913, Lief. 6, p. 311. 



Key to the Species of the Genus Petasometra. 



a 1 10 — 14 arms; 20 — 29 (usually 20 — 25) cirrus segments (Flor es and 



Amboina . . clarae 



a 3 over 20 arms; 28 — 31 cirrus segments (western Australia). . . . helianthoides 



1. Petasometra clarae (Hartlaub). 



Hartlaub. Nova Acta der Ksl. Leop.-Carol. deutschen Akad. der Naturforsch., vol. 58, 1891, 

 N u 1, p. 41, pi. 2, fig. 19 {Antedon clarae). 



Stat. 50. Bay of Badjo, west coast of Flores. 40 Metres. 3 Ex. 

 Stat. 231. Amboina. 3 Ex. 



Of the three specimens from Stat. 50 one has 11 arms 85 mm. long; one IIBr 1 series 

 is present, the IIBr axillary being supported equally by the IBr axillary and by the outer side 

 of the IBrj-, another has 10 arms 85 mm. long and cirri 13 mm. long composed of 20 — 22 

 segments; the dorsal pole of the centrodorsal is circular, slightly concave, 2 mm. in diameter; 

 the cirrus sockets are arranged in a single regular crowded row; the colour is dark brown, 

 the cirri and centrodorsal light yellow brown ; the IBr series and first brachials are white ; there 

 are one or two distinct white patches on individual arms; the third has 10 arms 85 mm. long; 

 the cirri are VII, 19 — 20, 12 mm. long; the dorsal pole of the centrodorsal is slightly concave, 

 circular, 2 mm. in diameter; the cirrus sockets are arranged in a single perfectly regular 

 crowded row. 



These specimens differ from the large individual from Amboina in having slightly fewer 

 cirrus segments, and in having P.. proportionately smaller; but both of these differences are 

 directly correlated with the smaller size. 



One of the examples from Amboina has 10 arms 120 mm. long; the centrodorsal is 

 discoidal, the dorsal pole large, circular, slightly concave, 2.6 mm. in diameter; the cirrus 

 sockets are arranged in a single perfectly regular marginal row; the cirri are XIV, 26 — 29, 

 17 mm. long, rather stout; owing to the very crowded condition of the cirrus sockets, which 

 are all in one regular row, the first segment of the cirri, as viewed dorsally, is very narrow ; 

 from this segment the cirrus increases in diameter to the fourth, which is at least three times 

 as wide as the first, and then tapers almost imperceptibly to the tip; all of the cirrus segments 

 are approximately equal in length, short, about twice as broad as long; the lateral margins of 

 the segments in the proximal half of the cirri are strongly bent, but those in the distal half 

 are straight; beginning- on the second or third there is a straight serrate transverse ridge, at 



fc> 1 ö O ö O ' 



SIBO GA- EXPEDITIE XLIl£. 15 



