A MONOGRAPH OF THE EXISTING CRINOIDS 141 



Syzygies occur between brachials 3+4, again from between brachials 16 + 17 to 

 between brachials 19+20 (in 1 case also between brachials 5 + 6), and distally at inter- 

 vals of about 12 or 14, decreasing later to 6 or 9, muscular articulations. 



P x is 18 mm. long, stouter than P 2 though not markedly so, tapering evenly from 

 the base to the tip; it is composed of 25 segments which are all about twice as long as 

 broad, sharply carinate dorsally, and also produced ventrally into a rounded carination. 

 P D is similar to Pl P 2 is 10 mm. long, much less stout than P,, tapering evenly from the 

 base to the tip, with 15 segments of which the first 4 are broader than long and those 

 following are about as long as broad, gradually becoming longer than broad. The 

 segments have a spinous dorsal carination which is more or less overlapping, and their 

 ventral distal angles are produced so as to give the ventral profile a strongly serrate 

 appearance. The following pinnules are similar but gradually decrease in length, P 5 

 being 7 mm. long and the 2 succeeding of about the same size, then gradually mcrease 

 again, the component segments at the same time becoming smoother and more regular. 

 The distal pinnules are 15 mm. long with 20 segments of which the first is short and 

 crescentic the second is trapezoidal, not so long as broad at the base, and the remainder 

 are about half again as long as broad, becoming about twice as long as broad distally 

 The distal pinnules are strongly prismatic, the prismatic ridge bearmg a narrow hue of 



fine spines. . 



Locality —Albatross station 3985; Hawaiian Islands, off Kaui; Hanamaulu ware- 

 house bearincr S 53°30' W., 6 miles distant; 786-872 meters; bottom temperature 4.4 

 C • gray sand°, Foraminifera, and shore deposit; June 10, 1902 [A. H. Clark, 1908, 1909, 



1911 1912 1915, 1916, 1918, 1949; Gislen, 1934] (1, U.S.N.M., 22687). 



History —Thalassometra gigantea was described in 1908 from a single specimen 

 from Albatross station 3985; later in the same year its proximal arm structure was de- 

 scribed in detail and explained (see Part 2, page 105, and figures 145, 146 page 83). 

 In two other papers published in the same year this species was said to belong to a 

 group characteristic of the oceanic areas. In my revision of the family Thalassometndac 

 published in 1909 gigantea was listed as a species of Thalassometra. In 1911 Ihulasso- 

 metra annandalei, originally described in the genus Crotalometra, was transferred to 

 Thalassometra in which genus it was said to occupy a position near Th. gigantea, and in 



1912 7% gigantea was compared with Th. magna, sp . nov. In my memoir on the crinoids 

 of the Indian Ocean published in 1912 Thalassometra gigantea was listed and the syn- 

 onymy and range were given. In my memoir on the crinoids of the Antarctic published 

 in 1915 the ornamentation of this species was compared with that of Anthometra adnani. 

 In 1916 Thalassometra gigantea was made the type of the new genus O^anometra. In 

 my memoir on the unstalked crinoids of the Siboga expedition published in 918 Oceano- 

 metra gigantea was listed, and the synonymy and range were given Its relationship to 

 0. magna was discussed. In 1934 Prof. Torsten Gislen discussed the arm structure of 

 this species. 



