REPORT ON THE CRINOIDEA. 313 
The disk is only partially visible, but seems to have a tolerably regular pavement of 
small plates. Arm-groove exceedingly narrow, the ambulacral plates being limited to the 
pinnule-bases. The pinnules have well defined covering plates with occasional faint 
indications of side plates. 
Colour in spirit, brownish-white. 
Locatity.—Station 122, August 10, 1873; lat. 9° 5’ N., long. 34° 50’ W.; 350 fathoms; 
red mud. One specimen. 
Remarks.—The leading characters of this elegant species were well described by Sir 
Wyville Thomson in The Atlantic. Its nearest allies are Pentacrinus miilleri (Pl. XIV.), 
Pentacrinus wyville-thomsoni (Pl. XVII. fig. 1), and Pentacrinus alternicirrus 
(Pl. XXV.), all of which it resembles very closely in the regularity and grouping of the 
arm-divisions. The stem, however, is totally different from that of Pentacrinus wyville- 
thomsoni with its long internodes, and the number of arms is also greater than is usually 
the case in this species. Pentacrinus miilleri and Pentacrinus alternicirrus approach it 
most closely, having relatively short internodes; but the arrangement of the cirri on the 
stem of the latter species distinguishes it at once. Pentacrinus maclearanus closely 
resembles some specimens of Pentacrinus miilleri in the shape of the nodal joints; but, 
apart from the characters of the internodes, it is readily identified by the unusual 
shortness of its lowest pinnules and the more rounded form of the joints in the later ones. 
The close approximation of the nodal joints, and the downward curvature of the 
cirri, together with the slight downward extension of the basals and the grouping of the 
arms, are of interest as recalling the Liassic Hxtracrinus briareus. 
Only four cirri are present at one of the nodes, the fifth socket being totally absent. 
This indicates a variation in the direction of Pentacrinus alternicirrus, which has only 
two or three cirri at each node (Pl. XXVI. figs. 1-3). 
4. Pentacrinus wyville-thomsoni, Jeffreys (Pl. XVII. figs. 2-6; Pls. XVHI.—XXIV. ; 
Pl LVil; fee): 
1870. Pentacrinus Wyville-Fhomsoni, Jeffreys, Proc. Roy. Soc., 1870, vol. xix. p. 157. 
1872. Pentacrinus wyville-thomsoni, Wyville Thomson, Proc. Roy. Soc. Edin., vol. vii. p. 767; and The 
Depths of the Sea, p. 444. 
Dimensions. 
Total length, . : : ‘ 3 ‘ . 24:00 cm. 
Longest stem, rounded off at een node: : . ; c . 155-00 mm. 
Shortest stem, rounded off at fifth node, 5 : ‘ : ~ S0;000%; 
Diameter of stem, : : ; ‘ : ‘ : 3°50) 5, 
Longest cirrus (nineteen ite)! : ; d 3 : 3» 24:00) 55 
Diameter of calyx, 3 A ; : ; : c ; ‘205s 
Diameter of disk, F E : : . : . OSD ss 
Length of arm (seventy Aine : : : LOO; OOM 
Length of pinnule on first free brachial (ten wountay é : - ce AKONONO) 
Length of pinnule from middle of arm (twenty-one joints), 5 BEE) gy, 
(ZOOL. CHALL, EXP,—PART XXxU,—1854.) Ti 40 
