264 THE VOYAGE OF H.M.S. CHALLENGER. 



relatively to their width, than in Rhizocrinus lofotensis, while the third brachial is oblong 

 and not trapezoidal, so that there is no sudden narrowing of the arm at the syzygy 

 between the third and fourth brachials. The shape of the arm-joints too, especially of 

 those which bear pinnules, is not the same in the two species ; while the pinnules them- 

 selves, and more particularly those on the proximal parts of the arms, differ very 

 considerably in appearance, those of Rhizocrinus rawsoni having broad lower joints. 



The visceral mass of Rhizocrinus lofotensis is relatively lower than that of Rhizocrinus 

 rawsoni, in which it is supported by the first six brachials (PL X. fig. 20) ; while in 

 Rhizocrinus lofotensis the ambulacra leave the peristome at the level of the second 

 brachials, on to which they pass. 



The stem-joints of Rhizocrinus rawsoni are relatively shorter and thicker than those 

 of Rhizocrinus lofotensis, in which the length is three times the width, and the radicular 

 cirri at the base of the stem are much more numerous in this species than in Rhizocrinus 

 raivsoni. In fact there are no radicular cirri whatever in one of the Challenger 

 specimens of Rhizocrinus rawsoni, and only two, borne upon the first joint above the 

 root, in one of those dredged by the " Porcupine." In correspondence with this, the root 

 of Rhizocrinus rawsoni is more like that of Baihycrinus, the lowest stem-joint giving 

 rise to three or more stout branches, which themselves eventually subdivide and bear 

 radicular cirri (PL X. fig. 15). This condition appears to be comparatively rare in Rhizo- 

 crinus lofotensis, in which the lowest stem-joint is often provided with from five to nine 

 slender cirri, but does not give attachment to a spreading root. 



The longest cup yet known in Rhizocrinus rawsoni was found in some individuals 

 which were dredged by the " Travailleur " in 1882, at a depth of 1900 metres (1000 

 fathoms), off Cape Blanc, on the coast of Morocco, and were referred by Prof. Perrier 

 to a new genus Democrinus} The cup is singularly elongated in form, as will be seen 

 by comparing the measurements kindly furnished me by Prof. Perrier, with those 

 given below for the Challenger, " Blake," and " Porcupine " specimens. 



Democrinus Parfaiti, Terriei = Rhizocrinus rawsoni, Pourtales. 



Dimensions. 



Length of the calyx from the terminal furrow to the first stem-joint, . 

 Maximum diameter of the calyx, ..... 



Height of the radials, ...... 



Diameter of the stem-joints, ...... 



Length of the stem-joints, ...... 



The basals of this type thus form a cup 9 mm. high from its lower extremity to the 

 constriction at the level of the basiradial suture ; while its maximum diameter is not 

 more than 2 mm., twice that of the stem-joints. 



^ Comptes rendus, t. xcvi., 1883, p. 450. 



