A MONOGRAPH OF THE EXISTING CRINOIDS 177 



segment has a slight projection on its distal dorsal edge that becomes a spiny keel on the 

 short outer segments. 



The radials are just visible. The IBr t are nearly oblong, not very convex, and are 

 barely united laterally. The IBr 2 (axillaries) are about twice as long as the IBri, 

 broadly pentagonal, with slight backward projections. The elements of the IBr series 

 and first two brachials have sharp straight edges fringed with spines and very slightly 

 flattened sides. Professor Gisl6n noted that the spines on the ossicles are confined 

 almost exclusively to their borders ; there are two spines on the central dorsal surface. 



The 10 arms are probably 30 or 35 mm. long. The first two brachials are nearly 

 oblong. Those following are obliquely quadrate and are as long as, or longer than, broad. 



Syzygies occur between brachials 3+4, between about brachials 14+15, and 

 dis tally at intervals of from 3 to 5 muscular articulations. 



PI is not much longer than P a and consists of about 12 segments of which the first 

 5 are rather expanded, with the inner edges a little cut away; all have tufts of small 

 spines along the dorsal border. The next two pairs of pinnules (P 2 and P b and PS and 

 PC) decrease slowly in length and become less spinous. The later ones are long, slender, 

 and tolerably smooth. 



The disk is 3 mm. in diameter, much incised and well plated. The pinnule 

 ambulacra have fairly definite side plates, and large sacculi are occasionally present. 



The color in alcohol is light brownish white. 



Locality. Challenger station 170A, near the Kermadec Islands, north of New 

 Zealand (lat. 2945' S., long. 17811' W.); 1,152 meters; bottom temperature 4.17 C.; 

 volcanic mud; July 14, 1874 [P. H. Carpenter, 1888; Hartlaub, 1895; Bather, 1897; 

 Hutton, 1904; A. H.Clark, 1907, 1908, 1909, 1912, 1913, 1918; Gisle"n, 1928] (1,B. M.). 



History. Antedon echinata was described and figured by Dr. P. H. Carpenter in 

 1888 in his report on the comatulids of the Challenger expedition, his material consisting 

 of a single specimen from station 170A. Dr. Clemens Hartlaub in 1895 discussed the 

 systematic and bathymetrical relationships of Antedon echinata; Dr. F. A. Bather hi 

 1897 compared it with the fossil Millericrinus recubariensis; and Capt. F. W. Hutton 

 in 1904 included it in his list of New Zealand echinoderms. 



In my revision of the genus Antedon published in 1907 echinata was transferred to 

 the new genus Thalassometra; in 1908 I twice mentioned Thalassometra echinata as 

 a member of a group characteristic of the oceanic area; and in 1909 in my revision of 

 the family Thalassometridae I listed it hi the genus Thalassometra. In my memoir 

 on the crinoids of the Indian Ocean published in 1912 I listed Thalassometra echinata 

 and gave the range, and in 1913 I noted that I had_ examined the type specimen hi the 

 British Museum. In my memoir on the unstalked crinoids of the Siboga expedition 

 published in 1918 echinata was included in the key to the species of Thalassometra, and 

 the synonymy and range were given. After exa'mining the type specimen at the 

 British Museum in 1925, Prof. Torsten Gisle"n in 1928 published a short note amplifying 

 the original description. 



