A MONOGRAPH OF THE EXISTING CRINOIDS 133 



Characters.— -The cirri are 20-23 mm. long with 35-40 segments. The three or 

 four segments before the penultimate have single median dorsal spines, these being 

 paired on the segments preceding. P, is small and weak, 5 mm. long with 14 or 15 

 segments. P2 is 8.5 mm. long with 14 segments. The pinnules following resemble 

 Pj, but slowly decrease in length. 



Remarks. — This species resembles C. suavis very closely, but it is easily dis- 

 tinguished by the fact that the spines on the cirri are double until near the tip. 



Locality.— Mabahiss station 10; Red Sea (lat. 13° 31' 00" N., long 42° 31' 00" E.) ; 

 55 meters; September 17, 1933 (1, B. M.). 



COLOBOMETHA DIADEMA A. H. Clark 



[See vol. 1, pt. 2, fig. 325 (proximal pinnules), p. 227; fig. 728 (disk), p. 346.] 



Colobometra diadema A. Ii. Clark, Proc. Biol. See. Washington, vol. 23, 1910, p. 7 (description; 

 Ugi, Solomon Islands); Rec. Australian Mus., vol. 9, No. 1, 1912, p. 84 (detailed description- 

 Ugi); Crinoids of the Indian Ocean, 1912, p. 165 (synonymy; Ugi); Unstalked crinoids of the 

 Siboga-Ex-ped., 1918, p. 123 (in key; range). — Gisl^n, Kungl. Svenska Vet.-Akad. Handl., 

 ser. 3, vol. 18, No. 10, 1940, p. 15. 



Diagnostic features. — -Pi is nearly as long as Po and is stiff and spinelike with 12 

 segments of which the fourth and following are about four times as long as broad; 

 P2 to P5 are similar, and are either of the same length or decrease slightly in length 

 distally; the cirri are composed of 33-40 segments of which the distal have paired 

 spines dorsally these being replaced by a single median spine on the antepenultimate; 

 the arms are about 70 mm. long; the distal ends of the pinnule and cirrus segm_ents 

 and of the brachials are armed with long and prominent spines. 



Description. — -The centrodorsal is small and discoidal with the bare dorsal pole 

 2 mm. in diameter and very shghtly concave. The cirrus sockets are arranged in a 

 single slightly irregular marginal row. 



The cirri are XI, 33^0, 22 mm. long. The first segment is short, the second is 

 nearly or quite as long as broad, and those following gradually increase in length to 

 the fifth, which is slightly (sometimes as much as one-third) longer than broad. The 

 segments as far as the tenth or twelfth are similar, and those succeeding gradually 

 decrease in length so that the distal segments are about one-third again as broad as 

 long. The second and following segments are rather strongly constricted centrally 

 and are provided with strongly produced and overlapping distal ends which are 

 bordered with prominent spines, both of these features dying away as the segments 

 become shorter. After about the tenth segment the spinous overlap dorsally resolves 

 itself into prominent paired spines which at the tip of the cirri move close together 

 and are replaced on the antepenultimate segment by a single median spine. The 

 opposing spine is large and prominent, triangular, median, about as high as the width 

 of the penultimate segment. The terminal claw is stout and strongly curved, and is 

 but httle longer than the penultimate segment. 



The radials are short, but extend well up into the angles of the calyx where they 

 entirely separate the bases of the IBr,. These last are oblong, shghtly more than twice 

 as broad as long, with a small spinous tubercle in the middle of the distal edge. The 

 IBr2 are broadly pentagonal, half again as broad as long, with the lateral edges not 

 quite so long as those of the IBr,. The inferior inner angle of those ossicles is slightly 



