308 THE VOYAGE OF H.M.S CHALLENGER. 



however, is not an immovable syzygy, as in Rhizocrinus, bnt the same peculiar form of 

 articulation as occurs between the second and third radials. 



" The individual represented in fig. 120 was obtained in Mid Atlantic, just north of 

 the equator (Station 106, 1850 fathoms). It was originally regarded by Sir Wyville 

 Thomson as identical with a species which was dredged in considerable abundance 

 in the Southern Sea (Stations 146, 147, 1375 and 1600 fathoms), and was named by 

 him Bathyerinus aldrichianus ; and the accompanying figure appeared under 

 this name in 'The Atlantic' Subsecpiently, however, Sir Wyville seems to -have 

 distinguished the two species, for the name Bathyerinus campbellianus occurs in his 

 handwriting on the plate in which the individual from Station 106 is represented. 



" A fourth species [Bathyerinus carpenter?) has since been dredged in the North 

 Atlantic by the Norwegian North Atlantic Expedition. The genus ranges in depth from 

 1050 to 2435 fathoms, while Rhizocrinus has not been found deeper than 955 fathoms, 

 and occurs at 80 fathoms in the Norwegian fjords. No fossil species of Bathyerinus are 

 known. 



" But for its resemblance to Rhizocrinus, it is probable that this genus would hardly 

 be regarded as related to the Apiocrinidae. The novel form (Hyocrinits 1 bethcllianus) 

 which was found associated with it at Station 147, is still more unlike the Pear-encrinite 

 type, and though originally referred to it, is rather to be regarded as representing a new 

 family altogether. The mode of attachment of the stem is unknown. Its component 

 joints are short, cylindrical, and differently marked from those of Bathyerinus. 



"The cup (fig. 122a, b) is composed of two alternating tiers of thin plates, the basals 

 below and the radials above. The latter are broad and spade-shaped, with a slight blunt 

 ridge running, up the centre and ending in a narrow articulating surface for an almost 

 cylindrical first brachial. The five undivided arms are composed of long cylindrical 

 joints deeply grooved within, and intersected by syzygial junctions. The first three 

 joints in each arm consist each of two parts separated by a syzygy ; the third joint bears 

 at its distal end an articulating facet, from which a pinnule sjnings. The fourth arm- 

 joint is intersected by two syzygies, and thus consists of three parts, and so do all the 

 succeeding joints ; and each joint gives off a pinnule from its distal end, the pinnules 

 arising from either side of the arm alternately. The proximal pinnules are very long, 

 running on nearly to the end of the arm, and the succeeding pinnules are gradually 

 shorter, all of them, however, running out nearly to the end of the arm, so that distally 

 the ends of the five arms and the ends of all the pinnules meet nearly on a level. 2 This 

 is an arrangement hitherto entirely unknown in recent Crinoids, and there is nothing 

 exactly like it in any fossil species. 



" The mouth is in the centre of the disk (fig. 122c) and protected by a pyramid of five 



1 Named after Hog Island, one of the Crozets near which it was found. 



2 The greater part of the preceding description, is taken verbatim from the original account of Hijocrinus which 

 was published by Sir Wyville Thomson, The Atlantic, vol. ii. p. 95, 1*77. 



