782 BULLETIN 82, UNITED STATES NATIONAL MUSEUM VOLUME 1 



Having now definitely associated Thaumatocrinus with the species of Pentametro- 

 crinus and of Decametrocrinus, it seemed to me evident that T. renovatus was nothing 

 more than the young of some species belonging to one of these two genera, most likely 

 Pentametrocrinus because of its 5 arms. So in 1911 and again in 1912 I referred to it as 

 "Pentametrocrinus, sp." 



Through the kindness of Profs. Ludwig Doderlein and Robert Hartmeyer, I had 

 received a magnificent series of the peutacrinoids of Promachocrinus kerguelensis from 

 the dredgings of the Gauss in the Antarctic, and from these I learned the hitherto un- 

 suspected fact that this species has at first 5 radials and 5 post-radial series, the other 5 

 radials first appearing as interradials quite similar to those of Thaumatocrinus between 

 the radials already formed. 



This discovery explained the true nature of Thaumatocrinus renovatus. It is 

 merely a very young specimen of the species described by Carpenter as Promachocrinus 

 abyssorum with the interradial radials only partly formed and with the beginnings of an 

 interradial arm on the posterior interradial. In 1912 Thaumatocrinus was definitely 

 identified as the young of Promachocrinus abyssorum, which, incidentally, had been 

 found at the same station with it. 



Since the Challenger dredged it in 1873 and 1874, this species has been found but 

 once, by the Gauss in 1903. The 2 specimens brought back by the Gauss were described 

 in 1915. 



THAUMATOCRINUS JUNGEESENI A. H. Clark 



[See vol. 1, pt. 1, fig. 113, p. 181] 



Thaumatocrinus jungerseni A. H. CLARK, Die Crinolden der Antarktis, 1915, p. 144 (a north Atlantic 

 species; nomen nudum), p. 149 (in key to the species of Thaumatocrinus; southwest of Iceland), 

 p. 150 (6144' N., 3029' W.; 1135 fms.; 3.0 C.); Unstalked crinoids of the Siboga-Exped., 1918, 

 p. 259 (in key; range); Smithsonian Misc. Coll., vol. 72, No. 7, 1921, pi. 13, fig. 49; The Danish 

 Ingolf-Exped., vol. 4, No. 5, Crinoidea, 1923, p. 13 (detailed description; Ingolf stas. 18, 97), 

 p. 44 (range) ; figs. 2-4, p. 14. GISLEN, Zool. Bidrag Uppsala, vol. 9, 1924, pp. 26, 42, 46, 83 

 (articulations). MORTENSEN, Handbook of the echinoderms of the British Isles, 1927, p. 23 

 (locality). KOEHLER, Les dchinodermes des mers d'Europe, vol. 2, 1927, p. 133 (listed). GISLEN, 

 Kungl. Fysiogr. Sallsk. Handl., new ser., vol. 45, No. 11, 1934, p. 17. 



Diagnostic features.- This is a small and slender species, with arms between 90 

 and 100 mm. in length and the centrodorsal from 2.5 to 3.0 mm. in diameter. The 

 relatively small centrodorsal bears XI-XIII (very rarely more) cirri, which are slender, 

 but not excessively so, with the third segment never more than twice as long as broad 

 and the fourth usually less than 4 times as long as the width of the expanded ends. 



Description. The centrodorsal is small, discoidal, usually rather thin, in the largest 

 individuals from 2.5 to 3.0 mm. in diameter at the base. The cirrus sockets are entirely 

 marginal, and are large and conspicuous. They may be arranged in a fairly regular 

 and uniform marginal row, but they are usually irregular in their disposition, forming 

 a very irregular marginal row. All of them, or very nearly all, are functional. In the 

 middle of the rather broad bare dorsal pole of the centrodorsal there is a rounded or 

 rounded-conical elevation which may be only very slightly developed so that the dorsal 

 pole appears almost flat, or may be so large that the entire dorsal pole rises into a blunt 

 cone; usually, however, it merely forms a prominent central tubercle. 



The cirri are IX-XVII (usually XI-XIII, rarely XIV or more) ,19-25 (usually 23-25, 

 most commonly 24, in fully developed individuals), from 35 to 48 mm. (averaging about 



