PART 5 A MONOGRAPH OF THE EXISTING CRINOIDS 777 



pretation of structure; young of Promachocrinus abyssorum) ; Crinoids of the Indian Ocean, 1912, 

 p. 32 ( = Pentametrocrinus, sp.), p. 250 (included in Penlametrocrinus) , p. 251; Smithsonian Misc. 

 Coll., vol. 61, No. 15, 1913, p. 67 (published references to specimens in the B.M.; Challenger stas. 

 147, 158; notes); Journ. Washington Acad. Sci., vol. 5, No. 3, 1915, p. 81 (Antarctic; range); 

 Die Crinoiden der Antarktis, 1915, p. 104 (collected by the Gauss), p. 106 (collected by the 

 Challenger; recorded as Thaumatocrinus renovalus -\-Promachocrinus abyssorum), p. 107 (in key to 

 antarctic crinoids), p. 149 (in key to the species of Thaumatocrinus), p. 150 (synonymy; Gauss 

 records; previous records), p. 170 (a deep water antarctic species; range), p. 171 (systematic and 

 geographical relationships), p. 193 (further discussion), pi. 9, figs. 1, 2; Unstalked crinoids of the 

 Sifcoga-Exped., 1918, p. 259 (in key; range). BATHER, Ann. Mag. Nat. Hist., ser. 9, vol. 1, No. 4, 

 1918, p. 299 (interradials). A. H. CLARK, The Danish Ingolf-Exped., vol. 4, No. 5, 

 Crinoidea, 1923, p. 17 (compared with T. jungersent) . GISLEN, Zool. Bidrag Uppsala, vol. 

 9, 1924, p. 26 (position of lowest pinnule) ; Ark. Zool., vol. 19, No. 32, 1928, p. 12 (notes) ; Rep. 

 Swedish Deep Sea Exped., vol. 2, Zool., No. 4, 1951, p. 56 (depth range). 



Taumalhocrinus renovatus PERKIER, Traite de zoologie, 1893, p. 858. 



Decamelrocrinus abyssorum MINCKERT, Zool. Anz., vol. 28, No. 13, 1905, p. 501. A. H. CLARK, Proc. 

 U.S. Nat. Mus., vol. 34, 1908, p. 216 (compared with rugosus); Mem. Australian Mus., vol. 4, 

 1911, p. 796 (locality); Journ. Washington Acad. Sci., vol. 2, No. 13, 1912, pp. 312-314 (adult of 

 T. renovalus; growth of the latter) ; Crinoids of the Indian Ocean, 1912, p. 33 (= Promachocrinus 

 abyssorum P. H. Carpenter, 1888), p. 248 (synonymy; localities). 



Pentametrocrinus, sp. A. H. CLARK, Mem. Australian Mus., vol. 4, 1911, p. 796; Crinoids of the Indian 

 Ocean, 1912, p. 32. 



Promachrocrinus abyssorum KOEHLER, Les e'chinodermes des mers d'Europe, vol. 1, 1924, p. 58 (depth). 



Thaumatrocrinus renovatus KOEHLER, Les e'chinodermes des mers d'Europe, vol. 1, 1924, p. 58 (depth). 



Diagnostic features. None of the six known specimens exceeds a size of 3.5 nun. 

 diameter of centrodorsal and 4 mm. length of the first 4 brachials; the centrodorsal is 

 low conical with a distinct apex and bears up to XX cirri, of which the basal 2 or 3 seg- 

 ments are short but the rest are probably several times longer than broad ; the proximal 

 pinnules are long, with over 15 segments, those of PI being not more than twice as long as 

 broad; the segments of the distal pinnules are progressively more elongated. 



Description [by A.M.C.]. The specimen from Challenger station 158, which is one 

 of the syn types of Promachocrinus abyssorum Carpenter, has the ceutrodorsal low conical 

 with the dorsal pole coming to a distinct peak. It is 3 mm. hi basal diameter and 

 1.2 mm. high. There are XIV cirrus sockets of which the rims are very prominent 

 except at the distal end. Three segments of the base of one cirrus remain attached. 

 They arc all short; even the third is shorter than broad. 



The first four brachials together measure 4 mm. in length. The width at the first 

 syzygy at 4 + 5 is 1.3 mm. The second syzygy is usually at 9+10. The distal inter- 

 syzygial interval is from 2 to 5 muscular articulations. The arms are all broken within 

 25 mm. distance from the calyx. The second brachial has a convex proximal side but 

 is barely longer than the first. It bears the first pinnule, which in 6 cases (5 of which 

 are adjacent) is on the right side and in 4 is on the left. The distal brachials are triangular 

 and become longer than broad. 



PI has 16+ short segments and measures 5 mm. 



P a with 17 segments may bear a small gonad or P 2 or P b may be the first genital 

 pinnule. 



P 2 has 12+ segments and measures 7 mm. The distal segments are about twice as 

 long as broad. The gonads are very short and thick; they extend for only 3 or 4 seg- 

 ments of the pinnule and end abruptly. 



