430 BULLETIN 82, UNITED STATES NATIONAL MUSEUM VOLUME 1 



149, pt. 2, 1937, p. 86; Res. Voy. Belgica, 1897-1899, Zoology, Crinoidea, 1937, p. 9; Discovery 

 Reports, vol. 18, 1938, p. 130 (monotypic; limited to Antarctic), p. 133; Rep. B.A.N.Z. Ant- 

 arctic Res. Exped. 1929-1931, ser. B, vol. 4, pt. 6, 1939, p. 196. CUENOT in Grassd, Traite" de 

 zoologie, vol. 11, 1948, pp. 39, 52, 71. GISLEN, Rep. Swedish Deep Sea Exped., vol. 2, Zool., 

 No. 4, 1951, p. 55 (depth range). 



Promachorinus (part) DE LoiyoL, Paleontologie francaise, ser. 1, Animaux inverte'bre's, Terrain jurassi- 

 que, vol. 11, pt. 2, 1889, p. 434. 



Antedon (part) VANHOFFEN, Zeitschr. Ges. Erdkunde, 1904, p. 369. 



Promacochrinus BELL, National Antarctic Exped., Nat. Hist., vol. 4, Echinod. 1908, p. 16. 



Promachocrinus (Promachocrinus) A. H. CLARK, Smithsonian Misc. Coll., vol. 61, No. 15, 1913, p. 60; 

 Die Crinoiden der Antarktis, 1915, pp. 105, 106, 128. 



Promachoerinus GISLEN, Zool. Bidrag Uppsala, vol. 9, 1924, p. 53. 



Diagnosis. A genus of Heliometrinae in which there are 10 radials and 20 arms; 

 the ceutrodorsal is conical; the arms are rounded dorsally; the brachials, of which the 

 longest are slightly broader than long, have spinous distal ends with often a greater or 

 lesser development of spines on the dorsal surface; and PI, which is similar to P 2 , has 

 40 to 50 segments. 



Geographical range. Shores of the Antarctic continent, the Graham Land pe- 

 ninsula, South Shetland and South Sandwich Islands, South Georgia, Bouvet, Kerguelen 

 and Heard Islands. 



Bathymetrical range. From 20 to 1080 meters. 



Thermal range. From 1.90 to +2.75 C. 



History.- Mentioned under the broad and comprehenisve name Comatnla by 

 von Willemoes-Suhm in 1874, this genus was first diagnosed by P. H. Carpenter in 

 1879. Promachocrinus as understood by Carpenter was characterized by the occurrence 

 of 10 radials superimposed upon 5 basals, and he included in this new genus not only 

 P. kerguelensis but also P. abyssorum and P. naresi which also have 10 radials, but 

 undivided arms. 



Carpenter wrote that there is a most remarkable general resemblance between 

 Promachocrinus kerguelensis and Heliometra glacialis and Solanometra antarctica, the 

 characters of the cirri, brachials, pinnules, and even of the gonads being very closely 

 similar in the 3 types, so that if nothing were known of Promachocrinus kerguelensis 

 but some fragments of its arms, one woidd unhesitatingly refer them to a species of the 

 "Eschrichti group," that is, of Heliometrinae. He also noted that in the other 2 species 

 which he assigned to Promachocrinus the arms remain undivided just as in Eudiocrinus 

 (including Pentametrocrinus). But the presence of 10 radials seemed to him to set 

 Promachocrinus, as he understood it, so entirely apart from all other comatulids as to 

 preclude the necessity of any close comparison between the component species and other 

 genera. 



In 1905 Dr. Wilhelm Minckert created the genus Decametrocrinus for the inclusion 

 of those species of Carpenter's Promachocrinus in which the arms are undivided, that is, 

 P. abyssorum and P. naresi, leaving kerguelensis the only species in the original genus. 

 He also created a new family, the Decametrocrinidae, for the reception of Proma- 

 chocrinus and Decametrocrinus. 



In 1908 I placed Promachocrinus, as understood by Minckert, in the family Ante- 

 donidae, and associated Decametrocrinus with Eudiocrinus in the family Eudiocrinidae. 

 On the discovery later in the same year that the 5-armed comatulids placed by Car- 

 penter in the genus Eudiocrinus belong in reality to two entirely different genera, Eudio- 



