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 face, 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 different 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. VIIa. figs. 6-8; Pl. IX. figs. 1, 2; 
Ply x foes, 2). 
1864. Rhizocrinus lofotensis, M. Sars, Forhandl. Vidensk. Selsk., p. 127. 
1868. Rhizocrinus lofotensis, M. Sars, Mémoires pour servir 4 la connaissance des Crinoides vivants, 
p. 38. 
1868. Bourgueticrinus Hotessiert, Pourtalés, Bull. Mus. Comp. Zodl., vol. i., No. 7, p. 128. 
1872. Rhizocrinus lofotensis, Wyv. Thoms. (pars), Proc. Roy. Soc. Edin., vol. vii. p. 770; The Depths of 
the Sea, 1873, pp. 447, 450. 
1874. Rhizocrinus lofotensis, Pourtalés, Ill. Cat. Mus. Comp. Zodl., vol. iv., No. 8, p. 28. 
1882. Rhizocrinus lofotensis, P. H. Carpenter, Bull. Mus. Comp. Zoél., 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 (Pourtalés), ; C : : 5 inches. 
Greatest length of stem (Sars), sixty-seven oe (2) : . : . 70mm. 
Greatest length of entire specimen (Sars), 5 : ; ‘ Sak OO) ass 
Greatest length of arm, about thirty-five joints (Sars), . : : st gl, 
Stem slender, bearing branching radicular cirri on its lower part, and ending below in 
a more or less spreading root. The cirri come off 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 
