216 BULLETIN 82, UNITED STATES NATIONAL MUSEUM 



NEMASTER GRANDIS A. H. Clark 



Plate 16, Figure 38; Plate 17, Figure 39 



Stella marina polyaclis, seu Luna marina Sbba, Thesaurus, vol. 3, 1758, p. 17, pi. 9, No. 3. 

 Nemasler grandis A. H. Clark, Proc. U. S. Nat. Mus., vol. 36, 1909, p. 504 (description; Albatross 

 Sta. 2146); The Danish Ingolf-Exped., vol. 4, No. 5, Crinoidea, 1923, p. 38 (range). 



Diagnostic features. — The long cirri, which are about 40 mm. in length and are 

 composed of 30-35 segments, seem to separate this form from A'', iowensis which it 

 otherwise resembles very closely. The arms are 24-31 in number, about 200 mm. 

 long. It is readily distinguished from N. ruhiginosa by the absence of the black 

 mediodorsal stripe on the arms, from A^. discoidea by the absence of the dark spot in 

 the middle of each pinnule segment, and from both by the greater size, more robust 

 build, and much longer and stouter cirri. 



Description. — The centrodorsal is thick discoidal with the bare polar area 5 mm. 

 in diameter and deeply concave. The cirrus sockets are marginal and are arranged 

 in 3 closely crowded alternating rows. 



The cirri are XXV-XXX, 30-35, about 40 mm. long, large and stout. The first 

 segment is short, about three times as broad as long; those following gradually in- 

 crease in length to the sixth or eighth which, with the 3 following, is about as long 

 as broad, then gradually decrease so that those from the twelfth or fifteenth onward 

 are about twice as broad as long, though the last 2 are again almost as long as broad. 

 Between the seventh and the twelfth there is a transition segment, proximal to which 

 the segments have a dull finely pitted surface and distal to which they have a highly 

 polished surface, the pits being widely scattered or absent, and dorsal processes. The 

 transition segment is not especially well marked. The segments proximal to it have 

 practically straight sides and no modification of the dorsal distal edge. The transi- 

 tion and following segments have the distal edge dorsally projecting as a transverse 

 ridge which is coarsely dentate, usually tridentate, and equal in length, transversely, 

 to about half the width of the segment. Distally the ridge gradually narrows, be- 

 coming bidentate, and on the terminal 4 to 7 segments resolves itself into a single 

 spine which on the antepenultimate becomes subterminal in position. All of the 

 transverse ridges appear as rather prominent spines in lateral view. The opposing 

 spine is prominent, though short, rather stout, and arises from the whole dorsal 

 surface of the penultimate segment. In length it is about equal to one-third the 

 width of that segment. The apex is subterminal or submedian. The distal edge 

 usually makes much less of an angle with the transverse diameter of the segment 

 than the proximal, giving the spine the appearance of leaning forward. The ter- 

 minal claw is considerably longer than the penultimate segment, stout basally, 

 slender distally, strongly curved proximally, but becoming nearly straight in the 

 distal portion. 



The ends of the basal rays are visible as low tubercles in the angles of the calyx, 

 but are with difficulty differentiated from the adjacent parts. 



The radials are concealed by the centrodorsal in the median Ime, but are visible 

 as rather conspicuous triangles in the interradial angles of the calyx. The apex of 

 these triangles separates the lower corners of the IBr,. 



