780 BULLETIN 82, UNITED STATES NATIONAL MUSEUM VOLUME 1 



Localities. Challenger station 147; between Marion Island and the Crozets (lat. 

 46 16' S., long. 48 27' E.); 2925 meters; temperature 1.22 C.; diatom ooze; December 

 30, 1873 [P. H. Carpenter, 1879, 1883, 1884, 1888; A. H. Clark, 1913, 1915] (2, B.M.). 



Gauss; Antarctic regions in the vicinity of Gaussberg; 2425 meters; February 24, 

 1903 [A. H. Clark, 1915] (1, Berl. M.). 



Gauss; vicinity of Gaussberg; 2450 meters; March 1, 1903 [A. H. Clark, 1915] 

 (1, Berl. M.). 



Challenger station 158; southwest of Melbourne, Australia (lat. 50 01' S., long. 

 123 04' E.); 3290 meters; temperature 0.83 C.; globigerina ooze; March 7, 1874 

 [P. H. Carpenter, 1879, 1883, 1884, 1888; A. H. Clark, 1913, 1915] (1, B.M.). Type 

 locality, but the surviving specimen is a syntype of Promachocrinus abyssorum and not 

 the type of renovatus. 



Geographical range. Antarctic and subantarctic regions from Marion Island and 

 the Crozets to south of Australia. 



Bathymetrical range. From 2425 to 3290 meters. 



Thermal range. From 0.83 C. to 1.22 C. 



History. Although the name Promachocrinus abyssorum was used twice by Car- 

 penter in 1879, it appeared in both cases as a nomen nudum, and the original description 

 of renovatus, published in 1884, and based upon the single 5-armed young individual 

 dredged by the Challenger at station 158, appeared before abyssorum was properly 

 described. 



This 5-armed specimen was described at great length and beautifully depicted in 

 two separate publications. Its peculiarities were brought out, and detailed comparisons 

 were made with various other species, especially among the fossils. The anomalous 

 features of this singular specimen, which seemed to separate it sharply from all recent 

 comatulids, and stalked crinoids as well, and to ally it with various of the older fossil 

 species, were the presence of 5 interradials separating the 5 radials, and the occurrence 

 on the anal interradial of a small tapering appendage of 4 or 5 gradually decreasing 

 segments. This appendage seemed to Carpenter to be of the same nature as the so- 

 called proboscis of Taxocrinus, Gnorimocrinus, Onychocrinus, etc. Further extraor- 

 dinary features were the presence of a complete circlet of basals similar to, but much 

 larger than, the basals of Atdecrinus, the presence of 5 large orals, and the occurrence 

 of a pavement of closely set plates between the orals and the radials occupying about 

 a fifth of the total diameter of the disk. But although Carpenter noted that the most 

 striking characters of the young Thaumatocrinus show a resemblance to early Paleozoic 

 crinoids, he remarked that it is, nevertheless, a comatulid, and therefore that it is more 

 than probable that this resemblance is not due to any genetic connection between them. 

 He mentioned the similarity of the arms and cirri to those structures in certain species 

 of Pentametrocrinus. 



Carpenter looked upon the occurrence of 10 radials instead of 5 in the comatulids 

 as a character of prime importance, outweighing any characters to be found in the cirri, 

 arms or pinnules. For the reception of the 10-rayed species he created the genus 

 Promachocrinus, in which he included all the species known to him which are now dis- 

 tributed between the genera Promachocrinus and TJiaumatocrinus. Thus it never 

 occurred to him that there could be any connection whatever between his 5-rayed 

 Thaumatocrinus renovatus and the 10-rayed Promachocrinus abyssorum found at the 

 same station. 



