A MONOGRAPH OF THE EXISTING CRINOIDS 179 



and sharply flattened laterally. They are only very moderately convex dorsally. The 

 IBr series are 4(3 + 4). 



The 11 arms are 80 mm. long. The first brachials are very short, four or five times 

 as broad as the median length, half again as long exteriorly as interiorly, in close 

 apposition and flattened against their fellows. The proximal and distal edges are 

 slightly thickened and densely beset with excessively fine spines, which are also found 

 more or less on the remainder of the dorsal surface. The second brachials are twice 

 as large as the first, wedge-shaped, twice as long exteriorly as interiorly; the edges 

 are slightly thickened and densely spinous, and the dorsal surface is more or less 

 spinous. On the outer lateral edges of both the first and second brachials the spines 

 become longer and are grouped on more or less prominent irregular bases. The first 

 syzygial pair (composed of brachials 3+4) is more than twice as broad as long, oblong 

 or slightly longer interiorly than exteriorly. The proximal and distal borders are 

 everted and densely spinous and there is a double row of spines along the syzygial 

 line, but otherwise the dorsal surface is devoid of spines. The next four brachials are 

 slightly wedge-shaped, about three times as broad as long, with the edges, both proxi- 

 mal and distal, rather thickly everted and densely spinous, and numerous spines on 

 the dorsal surface. The following brachials are triangular, about as long as broad, 

 with the entire dorsal surface beset with very fine spines which become longer on the 

 slightly produced, but not overlapping, distal edge. Distally the brachials become 

 wedge-shaped, as long as broad, and terminally longer than broad and ultimately 

 elongate, while at the same time the spines on the dorsal surface become longer, more 

 prominent, and more uniform in size, and are inclined so that they are directed diago- 

 nally outward from the arm. 



Pi is 8 mm. long with 20-21 segments and tapers evenly from the base to the 

 slender tip. The segments are at first broader than long, becoming about as long as 

 broad on the eighth and terminally longer than broad. The earlier segments have a 

 broad band of fine spines on the distal edge, and after about the eighth the whole 

 outer side becomes spinous in addition. 



P 2 is somewhat shorter and more slender than Pi and is composed of about 16 

 segments. P 3 is very slightly shorter than P 2 , with 16 segments. The genital pinnules 

 have the fourth-seventh segments slightly broadened. 



A T otes. — The specimen described is from south of the Nicobar Islands in 1,024 

 meters. A smaller specimen from southeast of Car Nicobar is quite similar to the one 

 described, though slightly smaller. It also has 11 arms, one IIBr 4(3 + 4) series being 

 present. All of the arms are broken off at the first brachial syzygy. The cirri are 

 XXII, 32-34, from 20 to 23 mm. in length. The apical cirri are smaller and shorter 

 than the peripheral, 15 mm. long with 26 segments. The basal cirrus segments have 

 finely spinous ends and a few short spines on the dorsal surface. 



Localities. — South of the Nicobar Islands; 1,024 meters; cable repair ship Patrol, 

 Eastern and Associated Telegraph Company [A. H. Clark, 1929] (1, B. M.). 



Southeast of Car Nicobar (lat. 7°15'24" N., long. 92°59'00" E.); cable repair 

 ship Patrol, Eastern and Associated Telegraph Company [A. H. Clark, 1929] (1, B. M .). 



Remarks. — This species is evidently most closely related to Th. midtispina of the 

 south Atlantic from which it differs in the larger size, greater number of cirrus segments, 



