A MOXOORAPH OF THE EXISTING CRINOIDS 285 



In Comatilia the mouth is central and the anal tube is small and marginal. 

 Sacculi are sparingly present. 



The single known species superficially suggests some of the small species of 

 Dorometra and related genera, and until it is closely examined its true affinities are 

 not suspected. 



COMATIUA IRIDOMETRIFORMIS A. H. Clark 



Plate 30, Figures 89-'92 



[See also vol. 1, pt. 1, fig. 235 (ventral view of cciitrodorsal), p. 249; fig. 326 (cirrus), p. 279; fig. 453 

 (dorsal view of radial pentagon), p. 355; pi. 2, figs. 528, 529 (young); pt. 2, figs. 13, 14 (cen- 

 trodorsal and radials), p. 15; fig. 183 (lateral view), p. 98; fig. 237 (arm), p. 197; fig. 264 (arm 

 and pinnules), p. 207; fig. 397 (covering plates), p. 245; figs. 592, 593 (pinnule tip), p. 303; 

 figs. 616-618 (comb), p. 317; fig. 687 (disk), p. 341; figs. 763, 764 (covering plates), p. 353; 

 figs. 803-805 (covering plates), p. 378] 



(Comatilia iridometriformis A. H. Clark, Proc. U. S. Nat. Mus., vol. 36, 1909, p. 366 (description; 

 Albatross station 2670); p. 497 (type of Comatilia); Ann and Mag. Nat. Hist., ser. 8, vol. 5, 

 1910, p. 361 (development of side and covering plates the result of a deep water habitat). — 

 Bather, Ann and Mag. Nat. Hist., ser. 9, vol. 1, No. 4, April 1918, p. 298 (interradials). — 

 A. H. Clark, Smiths. Miscell. Coll., vol. 72, No. 7, 1921, pi. 7, fig. 43; The Danish Ingolf- 

 Exped., vol. 4, No. 5, Crinoidea, 1923, p. 39 (range). 



Diagnostic features. — The absence of the second, third, and fourth pairs of pin- 

 nules, so that there are no pinnules between P, and Pa and P5 and P^, distinguishes 

 this species at once. It is a very small form, the arms being only 30 mm. in length; 

 the cirri are XVI-XXVIII, 9-10, from 5 mm. to 6 mm. in length, very slender and 

 delicate, with the longest segment about four times as long as broad with expanded 

 ends. 



The general appearance of this species suggests one of the small antedonids much 

 more than anj^ of the other species of Comasteridae; but the characteristic comasterid 

 comb is well developed. 



Description. — The centrodorsal is moderate in size, discoidal, with the bare 

 polar area flat, usually with a more or less developed low rounded median tubercle, 

 from 1 to 1.5 mm. in diameter. The cirrus sockets are usually in a single, but often 

 in a more or less partially double or even triple, marginal row. 



The cirri are XVI-XXVIII, 9-10, from 5 to 6 mm. long, exceedingly slender 

 and delicate. The first segment is short, about twice as broad as long, the second is 

 about twice as long as broad, the third and fourth are the longest, about four times as 

 long as broad, and the fifth is slightly shorter. The following segments gradually 

 decrease in length, the antepenultimate being about half again as long as its distal 

 diameter and the penultimate about as long as, or shghtly longer than, broad. The 

 second and following segments are strongly constricted centrally with expanded ends. 

 After the fourth the proximal ends become less and the distal more expanded, the 

 latter overlapping all around, but slightly more dorsally than ventrally, the dorsal 

 overlap, however, exhibiting no tendency to project anteriorly. The opposing spine 

 is terminal in position, directed obliquely forward, arising from the entire distal 

 half (or rather more) of the dorsal side of the penultimate segment, about equal to 

 one-half of the distal diameter of the segment in length, usually forking transversely 

 in its distal half, more rarely breaking up into a number of small spines. The ter- 



