REPORT ON THE CRINOIDEA. 259 



verticils of five cirri, just like that of a recent Pentacrinus ; and this is a much more 

 important morphological resemblance than the length of the basal plates. 



Then again the radials of Rhizocrinus are all in close lateral contact, while Belemno- 

 crinus has an anal plate intervening between two of the radials and resting on a basal. 

 It supports a heavy proboscis on its upper foce, while Rhizocrinus has a disk protected by 

 five insignificant oral plates. The arms of Belemnocrinus are ten in number, while 

 Rhizocrinus has only five. This, however, is unimportant ; but the arms of Belemno- 

 crinus bear two rows of pinnules alternately, while in some species these primary pinnules 

 bear alternating secondary ones, a condition totally unknown in any Neocrinoid. 

 Altogether, therefore, the structure of the arms of Belemnocrinus is very difi"erent from 

 that of Rhizocrinus, in which every joint has a syzygial surface at one of its ends ; though 

 it must be admitted that syzygies are plentiful in the arms of Belemnocrinus, as there 

 are some species, e.g., Belemnocrinus pourtalesi, in which " throughout the greater portion 

 of the arms every alternate joint is a syzygium." This character, however, and the 

 length of the basals are of minor importance compared to the intercalation of the anal 

 plate in the calyx and the nature of the articulation between the stem-joints, so that I 

 cannot in any way regard Belemnocrinus as an ancestral form of Rhizocrinus. 



1. Rhizocrinus lofotensis, M. Sars, 1864 (PL Villa, figs. 6-8; PI. IX. figs. 1, 2; 

 PI. X. figs. 1, 2). 



1864. Rhizocrinus lofotensis, M. Sars, Forhandl. Vidensk. Selsk., p. 127. 



1868. Rhizocrinus lofotensis, M. Sars, Memoires pour sorvir a la connaissance des Crinoides vivants, 



p. 38. 

 1868. Bourgueticrinus Hotessieri, Pourtalfes, BuU. Mus. Comp. Zool., vol. i., No. 7, p. 128. 

 1872. Rhizocrinus lofotensis, Wyv. Thorns, (pars), Proc. Roy. Soc. Edin., vol. vii. p. 770; The Depths of 



the Sea, 1873, pp. 447, 450. 

 1874. Rhizocrinus lofotensis, Pourtalfes, 111. Cat. Mus. Comp. Zool., vol. iv., No. 8, p. 28. 

 1882. Rhizocrinus lofotensis, P. H. Carpenter, P>ull. Mus. Comp. Zool., vol. x., No. 4, p. 173. 

 1884. Rhizocrinus lofotensis, P. H. Carpenter, Proc. Roy. Soc. Edin., vol. xii. p. 356. 



Dimensions. 



Greatest length of stem (Pourtalfes), ...... 5 inches. 



Greatest length of stem (Sars), sixty-seven joints {f) . . . .70 mm. 



Greatest length of entire specimen (Sars), . . . . . 80 „ 



Greatest length of arm, about thirty-five joints (Sars), . . . .11,, 



Stem slender, bearing branching radicular cirri on. its lower part, and ending below in 

 a more or less spreading root. The cirri come ofi" near the terminal faces of the lower 

 joints at the ends of their longer axes. The joints are markedly dicebox-shaped, and 

 nearly three times as long as wide. 



The calyx is smooth and obconical, of somewhat variable proportions. Basals two or 



