142 BULLETIN 82, UNITED STATES NATIONAL MUSEUM 



OCEANOMETRA MAGNA (A. H. Clark) 



PLATE 14, FIGURES 42, 43 

 [See also vol. 1, pt. 2, fig. 221, p. 171.J 



Thalassometra magna A. H. CLARK, Zool. Anz., vol. 39, No. 11/12, 1912, p. 425 (description; Siboga 

 station 251). 



Oceanometra magna A. H. CLARK, Journ. Washington Acad. Sci., vol. 6, No. 17, 1916, p. 606 (listed); 

 Unstalked crinoids of the Siboga-Exped., 1918, p. ix (relationship with 0. gigantea), p. 151 (in 

 key; range; detailed description; sta. 251), p. 274 (listed), pi. 22, fig. 57; Ann. Mag. Nat. Hist., 

 Ber. 10, vol. 10, No. 58, October 1932, p. 378 (history; listed), p. 382 (south of western Timor; 140-160 

 fathoms; notes), pi. 14. GISLEN, Kungl. Fysiograf. Sallsk. Handl., new ser., vol. 45, No. 11, 1934, 

 pp. 27, 28. 



Diagnostic features. All the ossicles of the division series and both the first and 

 second brachials bear median keels; no spines on the ossicles of the division series and 

 first two brachials except along the edges and on the crest of the keels; ossicles of the 

 division series with irregularly dentate produced lateral borders; dorsal surface of 

 earlier brachials sparsely spinous. A stout species with 21-28 arms 120-175 mm. long, 

 and the large and stout cirri 60-85 mm. long with 63-74 segments. 



Description. The centrodorsal is conical with the tip truncated, 5.5 mm. broad at 

 the base and 5.0 mm. high; the dorsal pole is about 1.5 mm. in diameter, approximately 

 flat and covered with fine papillae. The cirrus sockets are arranged in 10 columns of 

 usually four each, the two columns of each radial area being in close contact with those 

 of adjacent radial areas exteriorly, but separated in the midradial region by a bare 

 slightly concave area which is proximally nearly or quite as broad as the adjacent cirrus 

 sockets. 



The cirri are XXX-XL, 66-74, from 70-85 mm. long; the longest cirrus segments 

 are nearly or quite twice as long as broad. 



The ends of the basal rays are visible as dorsoventrally elongate tubercles bridging 

 over the very deep but very narrow subradial clefts. 



The radials are very short with a slight rounded median prominence and with a 

 few small teeth on the distal margin. The IBri are short, between four and five times 

 as broad as long, broadly V-shaped in a direct lateral view. The proximal and distal 

 edges are parallel, both slightly everted. The proximal edge bears along the margin a 

 few short irregularly placed spines. The distal edge bears, on either side of the median 

 line, about eight regular teeth which begin one third of the distance from the median 

 line and gradually increase in length to the anterolateral angle; this series of teeth is 

 continued inward toward the median line by small, and progressively smaller, spines. 

 The lateral edges are slightly produced and smooth. The anterolateral angles bear a 

 few prominent blunted spines. In the center of the ossicle there is a prominent and 

 sharp, though not especially high, median keel. The IBr 2 (axillaries) are broadly 

 rhombic, with the lateral angles truncated, about twice as broad as long; the lateral 

 edges are not quite so long as those of the IBri and are produced and irregularly and 

 coarsely spinous; the distal edges and the outer part of the proximal edge are slightly 

 everted and finely spinous; a prominent keel resembling that on the IBri runs nearly 

 its whole length. Nine IIBr series are present, all 4(3+4). These resemble the IBr 

 series and, like them, are prominently carinate; their lateral borders are produced and 

 irregularly denticulate or spinous. Nine IIIBr series are present, all 4(3 + 4), resembling 



