PART 5 A MONOGRAPH OF THE EXISTING CRINOIDS 681 



Trichometra delicata A. H. CLARK, Fisheries, Ireland, Sci. Invest., 1913, pt. 4, p. 3 (Helga sta. CXX). 



(Not T. delicata A. H. Clark, 1911). MORTENSEN, Handbook of the echinoderms of the British 



Isles, 1927, p. 38 (diagnosis; range); fig. 23, 1, p. 38. KOEHLER, Echinodermes des mers 



d'Europe, vol. 2, 1927, p. 133. 

 Orthometra hibernica A. H. CLARK, Journ. Washington Acad. Sci., vol. 7, 1917, No. 5, p. 130 (listed); 



Unstalked crinoids of the SAo^a-Exped., 1918, p. 258 (references); The Danish Ingolf-E\ped.. 



vol. 4, No. 5, Crinoidea, 1923, p. 42 (range), p. 57 (Ingolf sta. 44). MORTENSEN, Handbook of 



the echinoderms of the British Isles, 1927, p. 39 (diagnosis; habits); fig. 23, 2, p. 38 (cirrus). 



KOEHLER, Echinodermes des mers d'Europe, vol. 2, 1927, p. 133. 



Description. In the type specimen the centrodorsal is concealed by the cirri. 



The cirri are very numerous, probably about 13 mm. long, composed of 25 to 33 

 (usually nearer the latter) segments, of which the third to fifth are the longest, a third 

 again (rarely so much as a half again) as long as broad; the following segments decrease 

 in length, the third to fifth beyond these and those succeeding being about as long as 

 broad and the distal slightly, though not much, broader than long. The longer prox- 

 imal segments are slightly constricted centrally with rather prominent distal ends, and 

 the short distal segments have a median dorsal carination. 



The IB^ are not in contact basally, and their converging sides make an angle of 

 about 60 with those of the adjacent IBr,. The IBr 2 (axillaries) and the lower brach- 

 ials are widely free laterally. 



The elements of the IBr series and the proximal brachials have everted and serrate 

 distal edges. 



[NOTE BY A.M.C.] The arms of the holotype are all broken at the first or second 

 syzygy. The width at the first syzygy is 1.0 mm. and the length from the proximal 

 edge of the IBri to the second syzygy is about 7.0 mm. The pinnules are all broken. 

 PI has 7 + + elongated segments. 



Notes. The two other specimens from Helga station S.R. 151 resemble the one 

 described, but are smaller; one of them has the arms about 25 mm. and the cirri about 

 11 mm. in length. 



The single individual from Helga station CXX has the arms about 20 mm. long 

 and the cirri 7 mm. long, with 15 to 20 segments, of which the longest are three times as 

 long as the median width. At first I regarded this as an example of Trichometra deli- 

 cata, and so recorded it; but the small specimens of that species from Ingolj station 18 

 have the cirri much more slender with the segments much more elongated and with less 

 abruptly expanded ends. 



In the specimen from Huxley station 13 the cirri are about XXX, 25-26, about 9 

 mm. in length. The first segment has a dull surface, and the second seems to be a tran- 

 sition segment, similar to these segments in the cirri of the Thalassometridae. The 

 longest segments are only slightly longer than broad, with somewhat expanded distal 

 ends. The short distal segments have a dorsal keel and in lateral view their dorsal 

 profile is strongly and evenly convex. 



The IBr] are very short, about four times as broad as long. The IBr 2 are rather 

 low, slightly broader than long, the very short lateral borders making an angle of 

 about 90 with each other so that beneath the first brachials, which just touch their 

 neighbors outwardly, there is a considerable rhombic space between the IBr series. 



Localities. Huxley station 13; off Brittany (lat. 4807'30" N., long. 813' W.); 

 753 meters; sand, mud and hard ground; August 1906 (1, Mar. Biol. Assoc., Plymouth). 



