PART r. A MONOGRAPH OF THE EXISTING CRIXOIDS 751 



Carpenter's figures are quite good but additional cii-ri of rather unifomi length 

 appear to have been added. From tiie few remaining there seems to be much more 

 difference in size between the peripheral and apical cirri than i? shown. 



THAUMATOMETRA MINUTISSIMA (A. H. Clark) 



(See vol. 1, pt. 1, fig. 403, p. 311] 



Balhymelra minutissima A. H. Clark, Proc. Biol. Soc. Washington, vol. 21, 1908, p. 132 (listed; 



nomen nudum); Proc. U.S. Nat. Miis., vol. 34, 1908, p. 233 (description; Albatross sta. 2761'). 

 Trichomelra minutissima A. H. Clark, Unstalked crinoids of the Siboga-Exped., 1918, p. 247 (in key; 



range), p. 248 (references).— H. L. Clark, Bull. Amer. Mus., vol. 48, 1923, p. 149 (comparison). — 



MoRTENSEN, Handbook of the echinoderms of the British Isles, 1927, p. 38 (Brazil). — A. H. 



Clark, Mem. Soc. Cubana Hist. Nat., vol. 14, No. 2, 1940, p. 139, p. 141 (in key), p. 159. 



Diagnostic features. — Thaumatometra minutissima has only 12 to 15 cirrus seg- 

 ments, all of which are much elongated, the antepenultimate being over three times as 

 long as its proximal width and the penultimate about twice as long as broad; P3 

 bears the first gonad. The arms are about 13 mm. long, and the cirri 4 mm. in 

 tlie unique holotype. 



Description. — The centrodorsal is rather small, hemispherical, with the dorsal 

 pole furnished with several rather long spines; the cirrus sockets are closelj' crowded, 

 al)out 9 in each radial area. 



The cirri are about XLV, 12-15, 4 mm. long. The fkst segment is rather less than 

 half as long as broad, the second is over twice as long as its proximal diameter, in- 

 creasing rapidly in width from about the middle so that the breadth of the distal end 

 is nearl}'' twice that of the proxunal, and the third and following are very slender and 

 greatly elongated, increasing m breadth in each direction, but especially distally; 

 the fourth segment is similar to the third; the following gradually decrease in length, 

 their proximal ends becoming less and less enlarged, but their distal ends remaining 

 enlarged and funnel-shaped. The antepenultimate segment is over three times as 

 long as its proximal breadth, increasing in width from the base to the tip, most rapidly 

 in the outer two-thirds. The penultimate segment is about twice as long as broad with 

 a long triangular opposing spine arising from the whole of the dorsal surface, of which 

 the distal edge is perpendicular to the longitudinal axis of the segment. The termhial 

 claw is about equal in length to the penulthnate segment, moderately slender and mod- 

 erately curved. 



The radials are rather short in the median line with a very strongly concave distal 

 border and strongly produced interradial angles which, however, do not separate the 

 bases of the IBri. The IBr, are very short, their lateral edges, which are about twice 

 the middorsal length, being not much more than a third of their width. The distal 

 border is broadly fringed with fine spines, and the dorsal surface is find}' granulose. 



The IBrj (axillaries) are rhombic, broader tlian long, with the edges, especially 

 the anterior, strongly concave; the dorsal surface is finely granulose, and fine spines 

 are developed laterally. The ossicles of the IBr series, the first two brachials exteriorly 

 and the first three interiorly, are in close apposition with their neighbors and laterally 

 flattened, and have very finely spinous lateral borders. 



The 10 arms are 13 mm. in lengtii. The fii-st brachials are short, with the outer 

 edge rather longer than the inner and the distal edge strongly concave; the dorsal sur- 

 face is granulose, and the anterior border carries a strong fringe of very fine spines. 



