772 BULLETIN 82, UNITED STATES NATIONAL MUSEUM VOLUME 1 



Remarks. In 1937 Mr. Clark commented that both groups of fragments of this 

 species were taken together with broken specimens of Crotalometra sentifera. 



He also said that among the known forms of this family, these fragments approach 

 most closely in their structure the species of Thaumatocrinus, but the form of the gonads 

 seems to be unique so that the species will probably prove to belong to a different, 

 though related, genus. 



[NOTE BY A.M.C.] This part of the typescript was probably written before 1936 

 and it may be that Mr. Clark had second thoughts about giving a specific name to 

 such broken fragments, since he gave no name to the John Murray material. However, 

 it is obvious that this is a very distinctive form, and so I am leaving it under the name 

 proposed by Mr. Clark in the typescript. 



THAUMATOCRINUS RUGOSUS (A. H. Clark) 



Decametrocrinus rugosus A. H. CLARK, Proc. U. S. Nat. Mus., vol. 34, 1908, p. 213 (in key), p. 215 

 (description; Albatross sta. 4157); vol. 35, 1908, p. 126 (explanation of 9-rayed condition of the 

 type specimen); Crinoids of the Indian Ocean, 1912, p. 248 (range). 



Thaumatocrinus rugosus A. H. CLARK, Die Crinolden der Antarktis, 1915, p. 149 (in key), p. 150 

 (range); Unstalked crinoids of the Siboga-~E,xped., 1918, p. 260 (in key; range). 



Diagnostic features. The size of the unique type specimen is large, the arms being 

 between 200 and 250 mm. in length, and the centrodorsal 9 mm. in diameter at the 

 base. The centrodorsal is large, very much flattened, with a large bare polar area, 

 the second brachial is not appreciably longer than the first, and the proximal portion 

 of the arms is broad and very rugged, with strongly developed articular tubercles. 



Description. The centrodorsal is very low hemispherical, almost thick discoidal. 

 9 mm, in diameter at the base, with a large bare polar area, the surface of which is 

 studded with shallow pits. The cirrus sockets are closely crowded, arranged roughly in 

 3 or 4 rows, with about 4 sockets beneath each radial at the periphery of the centrodorsal. 



The cirri are about C, but all are broken off at the base. The longest fragment is 

 15 mm. long and consists of 7 segments, of which the first is very short, the second is 

 about as long as broad, the third is about three times as long as broad, and the re- 

 mainder are about four times as long as broad. The first two segments are almost 

 circular in cross section, but the third and following become laterally compressed. 

 The segments are oblong in lateral view. 



The ends of the basal rays are occasionally visible as slight tubercles beneath the 

 sutures dividing adjacent radials. 



There are 9 radials, the right posterior radius possessing one instead of the normal 

 two. The distal ends of the radials are even with the rim of the centrodorsal; their 

 distal borders are nearly straight, and are not produced interradially. 



The 9 arms appear to have been between 200 and 250 mm. long. The first 

 brachials are about twice as broad as long, closely united in the proximal half but widely 

 free beyond, so that a large U-shaped gap separates the distal halves of each two 

 adjacent first brachials. The second brachials are trapezoidal, half again as broad 

 distally as proximally, with the sides concave. The third brachials are nearly twice 

 as broad as long, with the distal and proximal edges equal to the distal edge of the 

 second brachials in length and the lateral edges strongly concave. The first syzygial 

 pair (composed of brachials 4+5) is about as long as its greatest width, with the lateral 

 edges strongly concave. The four following brachials are similar to the second; those 

 succeeding become wedge-shaped, smooth, nearly twice as broad as long, later more 



