336 BULLETIN 82, UNITED STATES NATIONAL MUSEUM 



Unidentifiable Species 



HETEKOMETRA DELICATA H. L. Clark 



Heteromelra delicata H. L. CLARK, Carnegie Inst. Washington Publ. 212, 1915, p. 105 (description; 



Friday Island) ; Echinoderm fauna of Torres Strait, 1921, p. 8 (secured by the Carnegie Exped.), 



p. 21 (Friday Island; not a Zygometra; possibly a young Amphimetra) , pi. 21, fig. 6, pi. 36, figs. 



4, a-/. 

 Zygometra punclata A. H. CLARK, Unstalked Crinoids of the Siboga-Exped., 1918, p. 60, footnote 1 



(includes Heterometra delicata). 



Description. The centrodorsal is relatively large, 2 mm. in diameter, low sub- 

 conical, with only the dorsal pole bare. 



The cirri are XV, 18-19, about 5 or 6 mm. long, long and rather stout, little 

 compressed distally. None of the segments arc longer than broad. The 10-12 distal 

 segments have conspicuous longitudinal dorsal crests or teeth. The opposing spine 

 is large. 



The elements of the IBr series and the first two brachials have small ventrolateral 

 processes. 



The 10 arms are about 25 mm. long and are composed of about 50-60 brachials, 

 which are more or less quadrate and are distinctly longer than broad on the distal part 

 of the arm. 



Sy/.ygies occur between brachials 3+4 and 9 + 10 and distally at intervals of 

 7-10 muscular articulations. 



PI is loss than 2 mm. long and is composed of 10 or 11 short segments of which the 

 basal are squarish. P a is similar but much smaller and has only six segments. P 2 is 

 similar to P! but is more than 2 mm. long and is rather stout with 10 segments, de- 

 cidedly the largest pinnule on the arm. P b is about equal to P t or a trifle larger but 

 has fewer segments. The distal edges of the segments of P 2 and P b are somewhat 

 flaring and very minutely spiny. P 3 is smaller than PI and has only six segments. 

 P c is similar but smaller. The pinnules succeeding become gradually larger until at 

 the middle of the arm they are about 3 mm. long and have 12 segments. None of the 

 basal pinnules are rigid and spikelike, but all have rather flagellate tips. 



The color is purple of a rather pale shade; the pinnules are yellowish at the tips 

 and the cirri are more or less white. Dr. Clark said that the colors are fairly well 

 preserved in alcohol. 



Remarks. The single specimen (M.C.Z., 587) upon which this species was based 

 was picked up on the sand flat on the southern side of Friday Island, Torres Strait, at 

 low tide, on September 13, 1913. Dr. Clark said that its relationships are obscure, for 

 although it seems to be a member of the family Himerometridae the outer brachials 

 preclude its being placed in Amphimetra, while the known species of Heterometra all 

 have more than 10 arms. It may perhaps need a new generic name of its own. 



The description of this new species reached me just as I was finishing the report 

 upon the Siboga collection, and after studying it, noting especially the short cirri, I 

 became convinced that Dr. Clark had been misled by a specimen of Zygometra punctata, 

 which I had first mistaken for Heterometra bengalensis (see page 123). So in a footnote 

 to Zygometra punctata as given in the key to the species of Zygometra I said that it 

 included Heterometra delicata H. L. Clark. Farther on, in a discussion of Z. punctata, I 

 said that Dr. Clark had redescribed this species under the name of Heterometra delicata, 



