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



in their turn the third radials or axillaries. Each of these bears two primary arms, 

 which either remain single or divide again more or less frequently ; but there are rarely 

 more than forty or fifty arms altogether, the forking taking place much less often than 

 in certain Comatuke. 



" The recent dredgings in the Atlantic and in the Caribbean Sea have yielded six species 

 of Pentacrinus; but only two were obtained in the Pacific, one of them, however, 

 occurring at such widely separated localities as the Kermadecs (Station ] 70) and the 

 Philippines (Station 214). At both these Stations, and also at others near them, several 

 species were met with of a new genus of Pentacrinidse, for which the name of Metacrinns 

 is proposed (fig. 118). It is a close ally of Pentacrinus, but instead of three, has four or 

 six radials, the second of which is a compound (syzygial) joint and bears a pinnule, as do 

 all the following joints below the axillary. The ' Vega' obtained a species of this genus 

 in 65 fathoms, in the bay of Yeddo, Japan, and eleven species were found by the 

 Challenger distributed among four Stations in the Pacific, between 500 and 630 fathoms, 

 Stations 192 and 214, being those where, like Antedon, it was found to be most 

 abundant. 



"The family Bourgueticrinidse is well represented in the Atlantic, though no member 

 of it has yet been obtained in the Pacific. Two species of the genus Rhizocrinus (fig. 1 1 9), 

 so well known on the Norwegian coast, have been found at several localities in the North 

 Atlantic (including Station 122), and in the Caribbean Sea, while there are several fossil 

 forms in the Tertiary deposits. The special interest of Rhizocrinus is due to its being a 

 dwarfed and degraded representative of the familiar chalk fossil Bourgueticrinus ettipticus, 

 and this is itself a similai'ly dwarfed member of the large group of Pear-encrinites or 

 Apiocrinidse, which are so abundant in the Bradford Clay and the other Jurassic rocks, 

 but seem to have died out before the middle of the Cretaceous period. The calyx of 

 Rliizocrinus is comparatively long, owing to the height of the basals, while the radials are 

 relatively small. These bear five simple arms, the joints of which are immovably united 

 to one another in pairs by a kind of suture, which is known as a syzygy. Only the upper 

 joint of each pair bears a pinnule, and there are no pinnules at all upon the first four or 

 five pairs. 



"Two species of Bathycrinus (fig. 120) were dredged by the Challenger in the 

 Atlantic, where it has the widest distribution of all the Stalked Crinoids. The genus had 

 hitherto been known only by a single immature specimen (fig. 121), which was brought 

 up in 1869 by the 'Porcupine's' dredge, from a depth of 2435 fathoms, in the Bay 

 of Biscay. Like Bourgucticrinus and Rhizocrinus, it is attached by a more or less 

 spreading root, and its dice-box shaped stem -joints are very similar to those of these two 

 genera. But the basals are quite low, and so closely united that the sutures between them 

 are invisible externally, except in young individuals. The radials, on the other hand, are 

 comparatively large, and are united by a muscular joint to broad second radials. To the 



