254 BULLETIN 82, UNITED STATES NATIONAL MUSEUM 



COMISSIA HORRIDUS (A. H. Clark) 



Plate 24, Figure 68 



Comaster (?) horridus A. H. CLARK, Proc. U. S. Nat. Mus., vol. 39, 1911, p. 533 (description; Alba- 

 tross station 5356). 



Comissia horridus A. H. CLARK, Ann. and Mag. Nat. Hist., ser. 8, vol. 7, 1911, p. 645 (listed, with 

 habitat); Crinoids of the Indian Ocean, 1912, p. 77 (synonymy; locality); Unstalked Crinoids 

 of the Siboga Exped., 1918, p. 19 (in key; range). 



Diagnostic features. The cirri are XVII, 14-15, 10 mm. long, with the longest 

 segment three or four times as long as broad. The arms are 55 mm. long. The ele- 

 ments of the division series have slightly prominent and finely spinous distal ends, 

 and the brachials have strongly overlapping and very spinous distal ends. 



Description. The centrodorsal is thin discoidal, with the bare polar area 1 mm. 

 in diameter. The cirrus sockets are arranged in a single closely crowded irregular 

 marginal row. 



The cirri are XVII, 14-15, 10 mm. long. The first segment is short, the second is 

 somewhat longer than broad, the third is twice as long as the width of its expanded 

 ends, and the fourth or fifth is the longest, two and one-half or three times as long as its 

 expanded distal end. The next segment is very slightly shorter, and usually a transi- 

 tion segment. The following segments decrease in length so that the distalmost 

 3 or 4 are about as long as broad and the penultimate somewhat broader than long. 

 The transition and following segments have minute median subterminal dorsal 

 tubercles. The terminal claw is half again as long as the penultimate segment, slender, 

 and moderately curved. The second and following segments have expanded ends. 

 The earlier segments are well rounded in cross section, after the fifth becoming flat- 

 tened laterally and much broader in lateral view. 



The distal ends of the radials are even with the edge of the centrodorsal in the 

 median line, but extend well up in the interradial angles of the calyx, where they 

 entirely separate the bases of the IBr : . The IBrj are oblong or slightly trapezoidal, 

 twice as broad as long, and widely separated laterally. The IBr 2 (axillaries) are pentag- 

 onal, about as broad as long, with the lateral edges slightly shorter than those of the 

 IBri and making with them a broadly obtuse angle. 



The 10 arms are about 55 mm. long. The first brachials are almost oblong, about 

 twice as broad as the exterior length, interiorly in contact basally. The second 

 brachials are of about the same size, but are longer exteriorly and shorter interiorly. 

 The first syzygial pair (composed of brachials 3+4) is about as long as broad. The 

 next 2 brachials are approximately oblong, half again as long as broad, and those 

 following become obliquely wedge-shaped, somewhat longer than broad, gradually 

 increasing in length distally, the terminal brachials being twice as long as broad. 

 The elements of the IBr series have slightly prominent and finely spinous distal ends. 

 After the sixth the brachials develop strongly overlapping and very spinous distal 

 edges. 



P, is 10 mm. long with about 39 segments, of which those after the fourth are about 

 as long as broad. The long terminal comb consists of about 25 long curved teeth 

 which are set closely together. P 2 is 6 mm. long with a similar comb. P 3 is6 mm. long 

 with a comb consisting of 18 teeth. P 4 is very slender, 6 mm. long, with a comb of 



