156 BULLETIN 82, UNITED STATES NATIONAL MUSEUM 



ships, and compared it with his new species Antedon agassizii. It was listed as Antedon 

 bispinosa by Sir Arthur E. Shipley in 1901, and by Dr. Otto Hamann in 1907. 



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

 to the new genus Thalassometra. In two papers published in 1908 Thalassometra bis- 

 pinosa was said to belong to a group characteristic of the oceanic area. In my revision 

 of the family Thalassometridae published in 1909 it was listed as Thalassometra bispinosa, 

 and it was included under this name, with the synonymy and range, in my memoir on 

 the crinoids of the Indian Ocean published in 1912. In a paper on the crinoids of the 

 British Museum published in 1913 I gave a brief note on the type specimen of Thalas- 

 sometra bispinosa, and listed it from the Antarctic, with the range, in 1915. In my 

 memoir on the crinoids of the Antarctic published in 1915 Thalassometra bispinosa was 

 discussed at considerable length. In my memoir on the unstalked crinoids of the 

 Siboga expedition published in 1918 bispinosa was included in a key to the species of 

 Thalassometra and the synonymy and range were given. Prof. Rene Koehler mentioned 

 this species in 1924, and in 1928 Prof. Torsten Gislen published additional notes on the 

 type specimen. 



THALASSOMETRA ELECTBAE John 



Thalassometra, n. sp., A. H. CLARK, Proc. U. S. Nat. Mus., vol. 40, 1911, p. 51; Crinoids of the Indian 

 Ocean, 1912, p. 208; Smithsonian Misc. Coll., vol. 61, No. 15, 1913, p. 70; John Murray Exped. 

 1933-34, Sci. Reports, vol. 4, No. 4, 1936 (Jan. 1, 1937), p. 101, 104, 105. 



Thalassometra electrae JOHN, Ann. Mag. Nat. Hist., ser. 10, vol. 20, August 1937, p. 161. 



Diagnostic features. The elements of the division series and lower brachials are 

 bordered with numerous coarse blunt spines, and the dorsal surface is studded with 

 large well spaced tubercles; the proximal pinnules are not spiny; and the cirri are 

 arranged in 10 definite columns on the centrodorsal. There are 10 arms (all broken 

 off at the base in the single known specimen), and the cirri are about 28 mm. long with 

 29^3 (usually about 40) segments. 



Description. The centrodorsal is a fairly high rounded cone. Its edge is produced 

 into slight interradial corners. The dorsal pole is large and rounded and is beset with 

 long coarse tubercles. The cirrus sockets are arranged in 10 evenly spaced columns, 

 2 in each radial area, and there are 2, exceptionally 3, sockets in each column. 



The cirri are XXII, 29-^13, usually about 40, about 28 mm. long. The first three 

 segments are broader than long, the third a little longer than the second, and the 

 second than the first. The fourth segment is constricted centrally and is about one 

 and one-third times as long as the least width. The distal edge of each of these four 

 segments is strongly produced forward and outward to form a cup around the base of 

 the next; the edge of the cup is denticulate. The fifth-seventh segments are slightly 

 more than twice as long as broad; on each cirrus one or another of them is a transition 

 segment with the distal third or quarter white and glossy, like the succeeding segments, 

 and the proximal part a dull yellow like the preceding segments. Distally the seg- 

 ments gradually decrease in length, at about the fifteenth becoming as broad as long; 

 beyond the fifteenth all are slightly broader than long. Toward the end of the cirrus 

 the segments become progressively smaller. The fifth-seventh segments show the 

 beginnings of a dorsal spine. This rapidly increases in size. By the ninth-twelfth 

 segments it is spinelike, arising from the distal fifth of the dorsal edge. It becomes 

 much stronger distally. About the twentieth-twenty-fifth segment it arises from the 



