172 BULLETIN 82, UNITED STATES NATIONAL MUSEUM 



The cirri are XX, 40 ; the longest proximal cirrus segments are nearly twice as long 

 as broad, and those in the distal half of the cirri are broader than long and overlap 

 dorsally so as to develop a sharp spinous keel. 



The radials are partially visible as narrow bands beyond the rim of the centrodorsal. 

 The IBri are short and oblong, rather convex in the middle of the dorsal surface. The 

 IBr2 (axillaries) are rhombic, with the lateral angles truncated so as to form sides nearly 

 as long as the sides of the IBri, and are about twice as broad as long. The elements 

 of the IBr series, the first two brachials, and the hypozygal of the first syzygial pair 

 have straight lateral edges, and small portions of their outer sides are flattened. The 

 edges of the elements of the IBr series are finely spinous. 



The 10 arms are probably about 40 mm. long and are composed of short quadrate 

 brachials which, as far as they are preserved, are finely spinous on the dorsal surf ace. 



Syzygies occur between brachials 3 + 4 and 13+14 and distally at intervals of 

 8-10 muscular articulations. 



P! is short and stout with about 15 segments of which the lowest are short, wide, 

 and slightly carinate, but not flattened laterally. The pinnules following diminish in 

 size to about the third pan- (P 3 and P c ) and then gradually increase in length, the seg- 

 ments becoming elongated. 



The disk is about 4 mm. in diameter and is much incised and well plated. Side 

 plates are fairly distinct on the pinnule ambulacra. Sacculi are apparently absent. 



The color in alcohol is light brownish white. 



The preceding description is adapted from the original description by Carpenter 

 with a few additions from his figure and from notes which I made after an examination 

 of the type specimen in London. 



Locality. Challenger station 232; Sagami Bay, Japan (lat. 3511' N., long. 13928' 

 E.); 631 meters; bottom temperature 5.0 C.; green mud; May 12, 1875 [P. H. Car- 

 penter, 1888; Hartlaub, 1895; A. H. Clark, 1907, 1908, 1909, 1912, 1913, 1915, 1918] 

 (1,B. M.). 



History. In his report on the comatulids of the Challenger expedition published 

 hi 1888 Dr. P. H. Carpenter described and figured this species under the name Antedon 

 latipinna on the basis of a single mutilated specimen from station 232 in 345 fathoms. 

 In 1895 Dr. Clemens Hartlaub discussed the systematic and bathymetrical relationships 

 of Antedon latipinna, and in 1907 I compared it, by insertion in a key, with a new 

 species, A. pubescens. 



In my revision of the genus Antedon published later in 1907 latipinna was referred 

 to the new genus Thalassometra, and in 1908 Tlialassometra latipinna was listed as one 

 of the crinoids of Japan. In my revision of the family Thalassometridae published in 

 1909 Antedon latipinna was listed among the species I was unable to place satisfactorily. 

 In my memoir on the crinoids of the Indian Ocean published in 1912 Thalassometra 

 latipinna was listed and the synonymy and range were given. In 1913 I published a 

 note on the type specimen which I had examined at the British Museum in 1910, and 

 in 1915 I discussed the range and its significance. In my memoir on the unstalked 

 crinoids of the Siboga expedition published in 1918 latipinna was included in a key to 

 the species of Thalassometra, and the synonymy and range were given. 



