REPORT ON THE CRINOIDEA. 321 
examined some of it with.the spectroscope, and found the usual bands of pentacrinin. 
A few specimens which have not been kept in the dark, but have been more or less 
exposed to light, have bleached completely white. 
5. Pentacrinus alternicirrus, n. sp. (Pls. XXV., XXVI.; Pl. XXVIL figs. 1-10). 
Dimensions. 
Total length, . ; = 5 : 6 , - 195 mm, 
Longest stem, rounded off at eeeentih node, . : ; : a Ges, 
Shortest stem, rounded off at eleventh node, . : ; : oi aie, 
Diameter of stem, é 5 5 6 5 F 2 A oa 
Longest cirrus (thirty joints), . : : 5 - . 5) PA 
Diameter of calyx, ; : ; : 5 . ; 5 Ds 
Diameter of disk, : : : : ; ; at hes 
Length of arm (eighty joints), : : : : LOOR 
Length of pinnule on first free Bevetaal (eleven Foirita) : : : ap EOS 
Length of pinnule from middle of arm (twenty-one joints), 5 : ay peal oes 
Stem smooth, short, and pentagonal, with rounded angles. Four to nine (usually 
five or six) internodal joints with crenulated edges. The nodal joints bear two and 
three cirri alternately, those at one node corresponding to the positions of the absent 
cirri at the nodes next above and below. Cirrus-sockets nearly circular, occupying the 
Whole height of the nodal joint, and extending upwards on to the supra-nodals.  Infra- 
nodals scarcely modified at all. The sockets are deeply hollowed and have prominent 
lateral rims, owing to the angles of the joint between them being produced outwards 
and rounded. Cirri composed of about thirty stout joints, the lowest of which, after 
the first four, are somewhat longer than their successors. The terminal claw is 
moderately large, and has no opposing spine, but the ventral surface of the later joints 
is a little uneven. The lowest limit of the interarticular pores is between the fifth and 
eighth nodes, 
Basals rhomboidal, extended slightly downwards, and produced laterally so as to 
meet their fellows in the re-entering angles of the calyx. The rays and their subdivisions 
in close lateral contact ; the joints as far as the sixth or eighth brachial having flattened 
sides. The two outer radials united by syzygy. About thirty (twenty-five to thirty-two) 
arms, usually six to each ray, the axillaries being limited to the outer divisions. Primary, 
secondary, and tertiary arms (the latter very rare) each of two joints united by syzyey. 
The two lowest brachials united in the same way, the epizygal bearing the first pinnule. 
Arms of about eighty smooth, oblong joints with syzygies at intervals of three to eight 
(usually five or six) joints. The ah one between the ninth and twenty-sixth brachials. 
First pinnules quite short, consisting only of ten or eleven joints, the lowest of which are 
broad and flat, and the later ones long and slender. This inequality gradually disappears 
as the pinnules increase in length towards the middle of the arm, where they are tapering 
(Z00L. CHALL. EXP,-—PART xxx11,—1884.) fi 41 
