168 BULLETIN 82, UNITED STATES NATIONAL MUSEUM 



THALASSOMETRA MARGARITIFERA A. H. Clark 



PLATE 17, FIGURE 55 



Thalassometra margaritifera A. H. CLARK, Zool. Anz., vol. 39, No. 11/12, 1912, p. 426 (description; 

 Siboga station 45); Unstalked crinoids of the Sihoja-Exped., 1918, p. 169 (in key; range; refer- 

 ences; description; station 45), p. 271 (listed), pi. 22, fig. 58. 



Diagnostic features . The elements of the division series and lower brachials have 

 the edges less strongly everted than in Th. hirsuta with the spinosity coarser, the spines 

 more uniform in size and more thickly distributed over the dorsal surface of the ossicles, 

 also larger 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 and is studded with 

 spines resembling those of the dorsal surface; and the cirri are arranged in 10 definite 

 columns on the centrodorsal. The 10 arms are about 95 mm. long, and the cirri 

 are 45 mm. long with 57+ segments. 



Description. The cirri are about 45 mm. long with somewhat more than 57 

 segments. 



The 10 arms are about 95 mm. long. 



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

 and distal edges of the elements of the IBr series and of the first two 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. 



Locality. Siboga station 45; eastern Flores Sea, north of the eastern end of Sum- 

 bawa (lat. 724'00" S., long. 11815'12" E.); 794 meters; fine gray mud with some 

 radiolarians; April 6, 1899 [A. H. Clark, 1912, 1918] (2, Amsterdam Mus.). 



History. Thalassometra margaritifera was described in 1912 from two specimens 

 dredged by the Siboga at station 45, and was redescribed and figured in 1918. 



THALASSOMETRA MARG1NATA A. H. Clark 



[See vol. 1, pt. 1, fig. 96, p. 159.] 



Thalassometra marginata A. H. CLARK, Crinoids of the Indian Ocean, 1912, p. 206 (detailed de- 

 scription; Investigator station 218); Unstalked crinoids of the Siboga-Exped., 1918, p. 167 (in 

 key; range), p. 170 (references); Journ. Linn. Soc. (Zool.), vol. 36, No. 249, April 1929, p. 654 

 (Nicobar Islands; notes). 



Diagnostic features. The elements of the division series and first two brachials 

 have the proximal and distal edges prominently everted and irregularly and coarsely 

 dentate, the dentations with numerous fine spines on their tips, and the lateral borders 

 perfectly plain, without spines or tubercles, and sharply, though narrowly, flattened 

 against their neighbors; and the cirri are arranged in 10 definite columns on the centro- 

 dorsal. There are 10 arms, and the cirri are 40 mm. long with 34-46 segments. 



Description. The centrodorsal is truncated conical with the sides slightly convex, 

 3.5 mm. broad at the base, 1.5 mm. broad at the dorsal pole, and 2.5 mm. long inter- 

 radially; the dorsal pole is covered with long coarse tubercles. The cirrus sockets 

 are arranged in 10 columns of 2 each which are in close lateral contact interradially 

 but are separated in the midradial line by an irregularly wedge-shaped smooth area 



