PART 5 A MONOGRAPH OF THE EXISTING CRINOIDS 679 



other species of Tonrometra such as T. remota the pinnule segments are cylindrical as 

 in laevis but those of the proximal pinnules are more numerous, numbering over 20. 



NEP1OMETRA LAEVIS (P. H. Carpenter) 

 FIGURE 39 



Antedon laevis P. H. CARPENTER, Challenger Reports, Zoology, vol. 26, pt. GO, 1888, p. 187 (description; 

 sta. 214), pi. 31, fig. 6. NICHOLSON and LYDEKKER, Manual of palaeontology, 1889, p. 411, 

 fig. 286B. A. H. CLARK, Smithsonian Misc. Coll., vol. 50, pt. 3, 1907, p. 353 (listed). HAMANN, 

 Bronn's Klassen und Ordnungen des Tier-Reichs, vol. 2, Abt. 3, 1907, p. 1579. A. H. CLARK, 

 Crinoids of the Indian Ocean, 1912, p. 33 (of P. H. Carpenter, 1888= Thaumatomelra laevis). 



Thaumatometra laevis A. H. CLARK, Proc. Biol. Soc. Washington, vol. 21, 1908, p. 128 (listed); Crinoids 

 of the Indian Ocean, 1912, p. 33 ( = Antedon laevis P. II. Carpenter, 1888), p. 247 (synonymy; 

 locality); Smithsonian Misc. Coll., vol. 61, No. 15, 1913, p. 65 (published references to specimens 

 in the B.M.; locality). 



Nepiometra laevis A. H. CLARK, Journ. Washington Acad. Sci., vol. 7, 1917, No. 5, p. 130 (listed); 

 Unstalked crinoids of the Szboja-Exped., 1918, p. 251 (in key; range), p. 252 (synonymy). GISLEN, 

 Ark. Zool., vol. 19A, No. 32, 1928, p. 12 (notes). 



Description [by A.M.C.]. The centrodorsal is concealed by the cirri but appears 

 to be hemispherical rather than conical. The cirri are crowded close together in alter- 

 nating rows. They number about XXX, with up to 30 segments, of which the longest, 

 the fifth or sixth, is about two-thirds again as long as broad. The relative length de- 

 creases in the distal segments, which are about as long as broad or may be shorter. 

 They have a slight dorsal keel but no dorsal spine. The opposing spine is small but 

 acute. 



The radials are short. The IBi 1 ! are convex and barely incised by the proximal 

 angles of the IBr 2 (axillaries) , which are slightly broader than long, rhombic in shape 

 with the proximal sides convex and the distal ones concave. The distal angle is slightly 

 produced. The IBrj are a little narrowed at the distal end and the axillaries project 

 laterally beyond them so that adjacent axillaries nearly touch. At the apex of each 

 lateral angle the ossicle is markedly rugous and on some axillaries a number of small, 

 sharp spines are developed. The first brachials are barelj 7 incised by the second ones. 

 As far out as the second syzygy the brachials are oblong in shape but broader than long; 

 the following ones become longer than broad. All the brachials are smooth. 



The 10 arms are all broken but were probably 25 to 30 mm. long. The length 

 from the proximal edge of the IBri to the second syzygy (9 + 10) is 6.4 mm., while the 

 width at the first syzygy (3+4) is 1.0 mm. Distally the syzygies occur at intervals of 

 3 muscular articulations. 



The longest remaining PI has 12 cylindrical segments, probably 3 or 4 more when 

 complete. The total length probably exceeded 5.5 mm. The first segment is short, 

 the second as long as broad and the following ones are progressively more elongated. 

 No P 2 is quite complete but one with 11 segments may lack only 1 or 2. The 11 seg- 

 ments total 4.3 mm. The second segment is already longer than wide and the succeed- 

 ing ones are also relatively longer than the corresponding segments of PI. As PI lies 

 alongside P 2 the adjacent segments are almost exactly comparable in their proportions, 

 for example the seventh segment of PI and the third segment of P 2 . Since the degree of 

 tapering appears to be similar, their tips were probably almost level. P 3 has at the 

 most 9 segments left, approximately 3 having been lost; when complete it would have 

 been about 4 mm. long. One P a is complete; it has 12 segments similar in proportions 

 to those of PI. The pinnules following P 2 are all more or less broken; their segments 



