PART 5 A MONOGRAPH OF THE EXISTING CRINOIDS 701 



Comatula rosacea (not of Fleming, 1828) W. Marshall, Die Tiefsee unci ihr Leben, 1888, p. 241 (New 

 England coast). 



Halhrometra tenetla A. H. Clark, Proc. Biol. Soc. Washington, vol. 21, 1908, p. 130 (listed); Amer. 

 Nat., vol. 42, No. 503, 1908, p. 719; Proc. U.S. Nat. Mus., vol. 43, 1912, p. 407 (confined to the 

 west Atlantic, never intruding on the territory occupied by [Poliometra] prolixa) ; Bull. Inst. 

 Ocfenogr. Monaco, No. 285, 1914, p. 20 (occurrence in water of less than 25 fms. in the Gulf of 

 Maine) ; Die Crinoiden der Antarktis, 1915, p. 203 (occurs in the Gulf of Maine; significance) ; The 

 Danish Ingolf-Exped., vol. 4, No. 5, Crinoidea, 1923, p. 43 (range), p. 56 (in key). — Mortensen, 

 Danmarks Fauna, No. 27, 1924, p. 23 (range; comparison with H. sarsi); Handbook of the echino- 

 derms of the British Isles, 1927, p. 41 (range; comparison with H. sarsi). — Hyman, The inverte- 

 brates, vol. 4, Echinodermata, New York, 1955, p. 114 (occurs in dense aggregations). 



Halhrometra denlata A. H. Clark, Proc. Biol. Soc. Washington, vol. 21, 1908, p. 130; Proc. U.S. Nat. 

 Mus., vol. 43, 1912, p. 408 (oast of New York); Smithsonian Misc. Coll., vol. 61, No. 15, 1913, 

 p. 63 (published references to specimens in the B.M.; localities). — F. W. Clarke and Wheeler, 

 U.S. Geol. Surv. Prof. Paper 90-D, 1914, p. 34 (inorganic constitutents of the skeleton); No. 102, 

 1917, p. 20 (same); No. 124, 1922, p. 17 (same). — Vinogradov, Mem. Sears Found. Mar. Res., 

 vol. 2, 1953, p. 256 (skeletal composition). 



Halhrometra tenella var. lenella Gisl^n, Ark. Zool., vol. 15, No. 23, 1923, pp. 12-14, p. 16 (in key), 

 pp. 17, 18, pp. 23-25 (synonymy; records; distribution); figs. 28-30, p. 10; Zool. Bidrag Uppsala, 

 vol. 9, 1924, p. 195; Vid. Medd. Nat. Foren. K0benhavn, vol. 83, 1927, p. 5 (abundance off 

 Massachusetts). 



Halhrometra tenella var. typica Koehler, Les ^chinodermes des mers d'Europe, vol. 2, 1927, p. 129. 



Diagnostic Jeatures. — See the key on p. 699. 



Description. — The centrodorsal is conical, the sides in profile slightly to markedly 

 convex, usually about as high as broad at the base or somewhat lower, more rarely 

 higher. The surface is entirely covered with very numerous closely crowded cirrus 

 sockets showing no regular arrangement which decrease in size, more evidently in the 

 apical half, to the dorsal pole. [Note by A.M.C. The side view figures of the centro- 

 dorsals of two specimens given on p. 67 of part 2 of this work show the cirrus sockets 

 in regular vertical columns. As the same is true of the other species illustrated on that 

 page, none of which belongs to the Zcnometrinae, it is probable that the artist falsely 

 regularized the positions of the sockets throughout.] There are usually five or six 

 peripheral sockets corresponding to each radial. The edges of the sockets and the 

 raised rims about the central canals arc rather prominent. 



The cirri are very numerous, L-LXXX, 24-33 (commonly 27-30), from 25 to 

 35 mm. (usually 28 to 30 mm.) in length, deUcate, slender and very brittle. The 

 apical cirri are 9 to 10 mm. long, with 18 to 20 segments. The peripheral cirri have 

 the first segment more than twice as broad as long, the second almost or quite as long 

 as broad, the third from half again to twice as long as its median diameter, the fourth 

 from two and a half to three times as long as wide, and the fifth, which is the longest, 

 four to five times as long as the median diameter; the sixth, or sixth and seventh are 

 of the same proportions as the fifth. The following segments gradually decrease in 

 length so that the last three to five are only slightly, and on the shorter cirri not at all, 

 longer than broad. The eloTigate earlier segments are constricted centrally with prom- 

 inent ends and similarly and evenly concave dorsal and ventral profiles; thougli very 

 evident, this constriction is not particularly strong. 



As the segments shorten distally, the expansion of the proximal ends gradually 

 disappears so that the short outer segments increase gradually in lateral diameter from 

 the anterior to the posterior ends, the dorsal profile being nearlj' straight and the ventral 

 slightly convex with the height of the convexity toward the distal end. The distal 



