1 86 



THE CRINOIDEA 



crinoidea (?) in which the arms fork once on IBr ; IBi-j and 2 and all 

 IIBr, except IlBr 3 , 6 , and 9 , are united in pairs by'trifascial articulation 

 (apud Carpenter, see Fig. XXIII. 2), which may become syzygial (apud 

 Danielssen) ; only the distal brachial of each pair bears a pinnule, and 

 there are no pinnules on the first few pairs ; the arms are loosely incor- 

 porated in the cup to half-way up IIBr :J ; lax has large muscle-fossae on 

 strong wing-like processes (cf. Fig. XVIII. 6). BB fused in adult to a 

 single discoidal ossicle ; RR also become closely united ; IBB obsolete. 



Interambulacral areas of tegmen contain 

 scattered small plates, and sometimes each 

 has a large plate, which may be an oral. 

 Columnals dicebox- shaped and twisted, 

 with bifascial articular surfaces ; each 

 said by Danielssen to be formed by 

 fusion of two columnals ; those in the 

 younger, proximal region are thin and 

 discoidal. The root branches. Genus 

 Bathyci-inus, Wyv. Thomson (1872; see 

 P. H. Carpenter, 1884, and Danielssen, 

 1892; syn. Ilycrinus, Danielssen & Koren, 

 1877), North Atlantic and Southern 

 Ocean, at 750-1500 fathoms (Fig. CV.). 

 Carpenter places this in the Bourgueti- 

 crinidae on the grounds of its resem- 

 blance to Rhizocrinus, while admitting 



FIG. cv. 



Iktthycrinus. 1, crown of B. Aldri- 

 chiunus, nat. size (after P. H. Car- 

 penter). 2, 3, and 4, B. Carpenteri 

 (after Danielssen). 2, new radials and 

 anus on an old base and stem, x 4 

 diani, 3 and 4, stein fragments, nat. 

 size, pn, pinnules ; rt, root cirri ; 

 .S'*], proximal region of stem; 67.,, 

 median ditto ; 8( 3 , distal ditto. 



FJO. CVI. 



Transverse section of the dot-Hal nervous 

 system in Bathycrinus Carpenttri, diagram- 

 matised from Danielssen. IR, interradial cords 

 which pass up between radial* ; JR, radial cords, 

 connected by re, the ring-commissure. 



that "the differences between the two genera are much greater than 

 their resemblances." If the absence of a proximale have the value 

 claimed for it by Wachsmuth & Springer, the two genera must go into 

 different orders. The interradial axial nerve-cords correlated with the BB 

 fork first within the sutures between RR, and, in Carpenter's opinion, the 

 basi-radial strands take the place of a ring-commissure ; but Danielssen 

 describes a ring-commissure (see Fig. CVI.). There 'are 3 water-pores 

 in each IR. The crown separates very easily from the BB and stem, 

 and may be replaced by a fresh crown (Fig. CV. 2). Sacculi occur. (See 

 also Fig. LIII.) 



