330 Mr. P. H. Carpenter on the Supposed 



arm-joints ; while the chambered organ in the interior of 

 calyx is the co-ordinating centre in which these impulses 



originate. 



This chambered organ is a constant feature in all Crinoids 



(perhaps even in all the Pelmatozoa) , as shown by the perfo- 

 ration or grooving of the calyx-plates for the reception of these 

 axial cords ; and the five primary interradial cords proceeding 

 from it are invariably situated in or upon the basal plates. 

 These plates, therefore, are of fundamental importance in the 

 morphology of a Crinoid ; and one would as soon expect to 

 find them absent as that their homologues, the genital plates, 

 should be missing from the calyx of an Urchin. Nevertheless 

 Quenstedt and De Loriol would have us believe that this is 

 really the case in the Eugeniacrinidee. I feel assured, how- 

 ever, that the basals are really present, though closely united 

 into the so-called " top stem-joint," just as in the Norwegian 

 variety of Rhizocrinus lofotensis. 



In the recent Bathycrinns this basal ring seems to be less 

 closely united to the radials above it than to the stem-joints 

 on which it rests ; for a considerable number of stems were 

 obtained by the ' Challenger,' retaining the basal ring at the 

 upper end, which had separated from the rest of the cup at 

 the basiradial suture. I have never heard of a similar case 

 occurring in Rhizocrimts j but the Eugeniacrinidae present 

 abundant instances of it ; for by far the larger number of the 

 symmetrical calyces oi Eugeniacrinm and Pkyllocrinw which 

 exist in* collections consist solely of the five closely united 

 radials. Thus out of twenty -six species of these two genera, 

 which are described by De Loriol, eighteen are known by the 

 radials and arm -joints only. In most cases the sutures sepa- 

 rating the radials can be traced over their conjoined under 

 surface as far as the opening of the central funnel. Conse- 

 quently, according to Quenstedt*, u man kann sich noch auf 

 das Bestimmteste tiberzeugen dass das interradiale (Becken) 

 fehlt." In some specimens, however, the radials rest on 

 what Quenstedt calls an unusually small stem-joint; and he 

 admits that " man konnte in solchen Fallen leicht versucht 

 werden, darin das eigentliche Basale zu vermuthen, allein es 

 fehlt jecle Spur von Zwischennahten." This supposed top 

 stem-joint is sometimes met with still attached to the radials 

 and also in an isolated condition, and Quenstedt admits its 

 resemblance to a ring of anchylosed basals. 



Quenstedt's argument that the basals of Eugeniacrinus 

 must be absent, because of the directions of the cleavage- 



* Petrefactenkunde Deutschlands, IV. Encriniden, pp. 396, 398, 402, 



