328 Mr. P. H. Carpenter on the Supposed 



of five closely united radials resting on an enlarged top stem- 

 joint and enclosing a kind of basal rosette, like that of 



Antedon. 



Pdortalfes, however, who had studied examples of Bhizo- 

 crinus lofotensis from the Gulf-stream, described the radials 

 as resting upon five elongated basals, the sutures between 

 which could only be seen with difficulty. But when the calyx 

 was forcibly split open, u the fractures followed the joints be- 

 tween contiguous basals, and between the latter and the first 

 radials " *• Pourtal&s further described another species of 

 Rhizocrinus (R. Rawsoni), in which the interbasal sutures are 

 quite as distinct as those between the radials. Nevertheless 

 these facts were quite overlooked by Ludwigfj though he 

 quoted Pourtales\s memoir. But, while retaining Sars's views 

 as to the subradial portion of the calyx being the top stem- 

 joint, he gave another and more correct interpretation of the 

 calcareous plate which Sara called the basal rosette ; and 

 instead of adopting Pourtalcs's analysis of the calyx, he de- 

 scribed as a basal ring a portion of the upper surface of the 

 calyx immediately surrounding the so-called " rosette 7 ' of 

 Kara. This supposed basal ring, however, is really the interior 

 of the widely open central funnel of the calyx, and is formed 

 by the united ventral faces of the radials ; while what Lud- 

 wig took for radial sutures separating the basals are really 

 nothing but the ventral furrows of the radials, which lead 

 downwards into the intermuscular furrows of their distal 

 articular faces. 



Thus, then, we may regard Pourtal&s as having proved that 

 in the recent species of Rhizocrinus the calyx consists of 

 basals and radials, just as in Apiocrinus and Bourgueticrinus, 

 though the sutures between the plates are not always visible. 



t f 'XI 1 il til 'I/ - **! " 



ZittelJ 



lof 



are generally visible externally ; but in the European variety 

 this is not the case, and sections through the decalcified calyx 

 do not reveal their presence, so that the anchylosis of the 

 plates must be very close. Similar variations appear in the 

 allied genus Bathycrinus. In describing B. gracilis Sir 

 Wyville Thomson § spoke of the lower portion of the head as 



* " Contributions to the Fauna of the Gulf-stream at Great Depths/' 

 Bull. Mug. Comp. Zool. vol. i. no. 7, pp. 128-130 ; and u Zoological Results 

 of the llassler Expedition/' ill. Cat. Mua Comp. ZooL no. viii. pp. M, 2». 



t Morphologische Studien an Kckinodermen, Hand i.pp. 120-422. 



% Loc. tit. pp. 892, 393. 



§ u On the (Jrinoids of the < Porcupine ' Deep-Sea Dredging Expedi- 

 tion/' Proc. Hoy. Soc, Ed. vol. yii. (1860-72) p. 772. 



