169 



including the more broadly rounded median keel, which 

 grade insensibly into those on the slightly everted borders 

 of these segments (Postillon Islands; 794 Met r es), margaritifera 



1. Thalassometra margaritifera A. H. Clark. 



A. H. Clark. Zool. Anzeiger, vol. 39, 1912, N° 11 12, p. 426 [Tlialassomctra margaritifera). 

 Stat. 45. 7°24'S., iiS°I5'.2E. Flores Sea. 794 Metres. 2 Ex. 



This species is very closely related to Th. hirsuta; the eversion of the proximal and 

 distal edges of the ossicles of the IBr series and of the first tvvo brachials is less marked than 

 in Th. hirsuta and the spinosity is coarser, the spines being more uniform in size and more 

 thickly distributed over the- dorsal surface of the segments; they are also longer, so that there 

 is less difference between the spines of the dorsal surface and those of the everted edges; the 

 median carination is more rounded than that of Th. hirsuta, and is studded with spines 

 resembling those of the general dorsal surface. 



The cirri are about 45 mm. long, with somewhat more that 57 segments: the arms are 

 about 95 mm. long, in hirsuta being 95 mm. to 100 mm. long. 



2. Thalassometra hirsuta A. H. Clark. 



A. H. Clark. Proc. U.S. National Museum, vol. 39, 191 1, p. 552 [Tlialassometra hirsuta). 



Stat. 85. o°3Ó'.5S., ii9°29'.5E. Makassar Straits. 724 Metres. 7 Ex. 

 Stat. 286. 8°5o'.2S., I27°2.2E. Timor Sea. 883 Metres. 1 Ex. 



A specimen from Stat. 85 may be described as follows : 



The centrodorsal is small, low, rounded conical ; the dorsal pole is thickly studded with 

 small more or less sharpened papillae; the cirrus sockets are arranged in ten columns, closely 

 crowded, of two sockets each . 



The cirri are XX, 60—64, 40 mm. to 45 mm. long; the longest proximal cirrus 

 segments are from two and one half to three times as long as broad; the eversion of the 

 distal edo-es of the segments begins on the fith or sixth. 



The dorsal surface of the ossicles of the IBr series and of the first two brachials is 

 uniformly and rather thickly covered with short fine spines; their proximal and distal edges are 

 everted and armed with very numerous fine spines which are more closely set and longer than 

 those on the dorsal surface; the IBrj ancl the proximal half of the median line of the axillary 

 bears a moderately sharp, though low, median keel which is studded with slender spines ; 

 more or less complete reduplications of this keel occur on the first two brachials; beyond the 

 first syzygy the spines become finer, shorter, mor-e thickly set, ancl more evenly distributed, as the 

 ends of the brachials become oblique gradually giving way the finely serrate longitudinal striations. 



The base of the animal is moderately compact, the outer edges of the ossicles of the 

 IBr series and lower brachials being straight and in close apposition. Rather small water 

 pores are present. 



SIBOGA-EXPEDITIE XLII b. 22 



