A MONOGRAPH OP THE EXISTING CRINOIDS 401 



and more delicate distally so that they taper less regularly, and they are considerably 

 shorter, while the cirri are very much longer with more numerous segments of which 

 the distal are much longer. I said that from the published description and figure I 

 had assumed that this form was allied to the species of Stephanometra with which it was 

 associated by Hartlaub and, as it differed materially from all the forms which I had 

 grouped in that genus, I had suggested the generic name Oxymetra for it. Examina- 

 tion of the specimen, however, showed that it has nothing to do with the species of 

 Stephanometra but instead is closely related to the species which I had groiiped in the 

 genus Selenemetra, especially to S. tenuicirra. 



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

 erinacea was placed in the family Stephanometridae, Selenemetra, and the species 

 included in it (finschii, aranea, gracilipes, and viridis) being assigned to the family 

 Mariametridae. 



In my report on the unstalked crinoids of the Siboga expedition, erinacea was 

 included in the key to the species of the genus Oxymetra but was not further considered, 

 as it was not secured by the Siboga. 



OXYMETRA TENUICIBBA (A. H. Clark). 



PLATE 43, FIGURES 195, 196 



Selenemetra tenuicirra A. H. CLARK, Ann. Mag. Nat. Hist., ser. 8, vol. 10, 1912, p. 32 (description; 



Siboga station 320); Smithsonian Misc. Coll., vol. 60, No. 10, 1912, p. 22 (nearest to Oxymetra 



erinacea; comparison) . 

 Oxymetra tenu-'cirra A. H. CLARK, Unstalked crinoids of the Siboga-Exped., 1918, p. vin (discovery 



by the Siboga and its significance), p. 98 (in key; range), p. 99 (detailed description; station 320), 



p. 276 (listed), pi. 19, figs. 37, 38. GISLN, Kungl. Fysiogr. Sallsk. Handl., new ser., vol. 45, 



No. 11, 1934, p. 33. 



Diagnostic features. Kesembling 0. erinacea but with the cirrus segments longer, 

 the longest about twice as long as broad and the distal about as long as broad; there 

 are 49 arms 150 mm. long and the cirri have 69-78 segments. 



Description. The cirri are XXXV, 69-78, from 55 to 70 mm. long, much slenderer 

 than those of 0. finschii, with much longer distal segments, which are nearly or quite 

 as long as broad, and also longer proximal segments, the longest of which are about 

 twice as long as broad. 



Each IIBr series bears two IIIBr series of which the inner bears an internal IVBr 

 series so that there are normally 10 arms to each ray arranged hi 2, 3, 3, 2 order. 



The 49 arms are 150 mm. long. 



PI is 11 mm. long, with 20 or 21 segments, which become about as long as broad 

 on the fifth or sixth, and twice as long as broad distally. P 2 is 12 mm. long, with 22 

 segments, resembling PI. P 3 is 10 mm. long, with 18 segments. P 4 is 7.5 mm. long, 

 with 13 segments and with the distal taper more marked than in P 3 . P 5 is 7 mm. long, 

 with 13 segments, slightly slenderer than P 4 , especially in the distal portion. The 

 distal pinnules are 8 mm. long, with 17 segments. 



Remarks. This species is very closely related to Oxymetra erinacea, from which it 

 differs chiefly in having slenderer cirri with much longer distal segments, which are 

 nearly or quite as long as broad instead of twice as broad as long or even broader as in 

 0. erinacea, and also longer proximal segments, the longest of which are about twice as 

 long as broad instead of only slightly, if at all, longer than broad. 



