PART 5 A MONOGRAPH OF THE EXISTING CRINOIDS 577 



record), p. 10 (Tegelthof station e; Jermak stations 77, 82, 80; Malygin station 16-b; collections 

 of 1929, 1930, and 1931, stations 48, 49, 56, 57, 58, 59, 60, 61, 62, 68, 71, 72, 77, 79, notes), p. 35 

 (stations 48, 49, 56-62, 71, 72, 79, Tegetthof, Jermak, and Malygin), p. 39 (distribution), pp. 41, 

 42, 44, 47 (distribution), pp. 49, 50, 54, 55, 63 (Sedow stations 48, 49, data), p. 65 (Sedow sta- 

 tions 56, 57, data), p. 66 (Sedow stations 58, 59, data), p. 67 (Sedow stations 60, 61, 62, data), 

 p. 69 (Sedow station 68, data), p. 71 (Lomonossow stations 71, 72, data), p. 72 (Lomonossow 

 station 77, data), p. 73 (Lomonossow station 79, data), p. 75 (Tegetthof station e, data), p. 76 

 (Jermak station 77, data), p. 77 (Jermak stations 82, 86, data), p. 78 (Malygin station 16b, 

 data). DJAKONOV, Les e'chinodermes des mers arctiques, Leningrad (in Russian), 1933, p. 22 

 (in key), p. 23 (general account; range); fig. 8, p. 23. SCHORYGIN, in Gaevskoy, Check list of 

 the fauna and flora of the northern seas of the U.S.S.R., 1948, p. 470 (notes; north Russian 

 distribution). 



Heliometra prolixa OORBUNOW, Trans. Arctic Institute, Leningrad, vol. 7, 1933 (in Russian), p. 50 

 (Witnej Bay, Blagopolutschja Bay). 



Antedon sarsi (not of Diiben and Koren) GORBUNOW, Trans. Arctic Institute Leningrad, vol. 8, 1933 

 (in Russian), p. 5 (Marenzeller's record), pp. 54, 75 (identity). 



Diagnostic features. The centrodorsal is subconical, about as high as broad at the 

 base, with up to about LXXX cirrus sockets, which are arranged in each radial area 

 peripherally in 4 columns and apically in 3 ; in small individuals and rarely in larger ones, 

 there are 3 columns of cirrus sockets in each radial area. The peripheral cirri are 

 very long, more than half the length of the arms (which are from 85 to 120 mm. in 

 length), only slightly curved, and composed of 32 to 50 segments, of which the distal 

 have the dorsal portion of the distal end slightly produced; the apical cirri are about 

 a third the length of the peripheral in large individuals, with about half as many seg- 

 ments. PI is greatly elongated, very slender, but stiffened, usually 3 times as long as 

 P 2 , composed of 25 to 45 segments, of which all but the basal 5 to 7 are greatly elongated 

 with spinous distal ends. The distal intersyzygial interval is 4 muscular articulations. 



This species has frequently been confused with the species of Hathrometra, with 

 Heliometra glacialis, and with Leptometra celtica. 



In the species of Hathrometra, which resemble it in pinnulation and are of the same 

 color, the cirrus sockets are arranged in crowded alternating rows instead of in columns, 

 and the distal intersyzygial interval is 3 muscular articulations. 



In Heliometra glacialis, which is bright yellow in life, sometimes with a tinge of 

 purple, PI is rather stout, composed of relatively short segments, and more or less flex- 

 ible; the centrodorsal is low, hemispherical, flattened dorsally; and the cirri, which are 

 stouter, have more prominent dorsal spines on their distal ends. 



In Leptometra celtica, which varies in color from green to white, the cirri, though 

 generally similar, are much less numerous; there are only 2 or 3 columns of cirrus sock- 

 ets in each radial area of the centrodorsal; and P 2 is as long as and resembles P,, being 

 greatly longer, instead of shorter, than P 3 . 



Description. The centrodorsal is large, subconical, commonly about 4 mm. broad 

 at the base and 4 mm. high, the sides in profile convex proximally but becoming straight 

 distally. At the periphery of the centrodorsal the cirrus sockets are typically arranged 

 in four columns in each radial area, the two outer of 5 or 6 sockets, the two central 

 of 2 each (in the smaller specimens of 1) merging into .a single column of 3 sockets, 

 so that, whereas in the proximal portion of the centrodorsal there are 4 columns of cirrus 

 sockets in each radial area, in the distal there are only 3. There is a slight tendency 

 to develop bare low ridges, bare spaces, or shallow grooves in the interradial lines. 

 Immediately about the dorsal pole there is an area in which the cirrus sockets are 



