OALAMOCKlIsUS DlOMKD.E. 15 



of the radiating grooves for the reception of the radial continuation of 

 the axial cord and of the longitudinal muscular fibres is shown in Plate 

 XIX. Figs. 2 and 4. 



The cavity for the chambered organ is entirely within the basal ring, 

 occupyiuo- the central part of the excavated basal ring above the opening 

 for the passage of tlie axial cord and tlie edge of the larger ring, from 

 ■which branch off in the grooves of the basal plates the forks of the axial 

 cord leading to the radials. 



In Apiocrinus the basals are grooved for the reception of the bifurcating 

 cords, and in Millerlcrinus Milleri the chambered organ is, according to 

 Carpenter, entirely upon the ventral aspect of the basals. 



The proximal face of the first radial (Plate XX. Fig. 5), by which it is 

 united to the basals, is a bevelled surface, which is somewhat irregular on 

 the inner face (Plate XX. Figs. 2 and 5), but with a sharp outer edge, 

 corresponding closely to the outlines of the basiradial sutures of the cor- 

 responding basals. It is united to the adjoining radials by a bevelled face, 

 similar to that of the distal face. The thickness of the first radial increases 

 rapidly towards its distal face (Plate XX. Fig. 4, rw, nv), from the sudden 

 development of the proximal and distal wedge-shaped projections rw and 

 rw' (Plate XX. Fig. 2), which serve as supports for the interradial liga- 

 mentary bundles (Plate XX. Fig. 9). 



The grooves which carry the axial cords on the ventral face of the radials 

 pierce the first radial in its upper third (Plate XX. Fig. 2), and come out 

 at the distal face in the central part of the ridge which separates the fossa 

 for the dorsal ligaments from the fossse for the interarticular ligaments and 

 the muscular fossaj (Plate XX. Fig, 3). 



The ridges separating the fossie for the interarticular ligaments from the 

 muscular fossae are somewhat indistinct, and there appear to be two such 

 fossse for the interarticular ligaments (Plate XX. Fig. .3). The interarticular 

 ligaments of the second radial (/^ Plate XX. Fig. 2) are much reduced in 

 importance, as is seen in the figure of the proximal face (Plate XX. Fig. 6). 

 There is no trace of a fossa for the interarticular ligament on the distal 

 face of the same radial (Plate XX. Fig. 7), but on one side of the axial 

 canal of the distal face of the third radial there is a marked fossa for the 

 interarticular ligament. 



Judging from the figures of the interior of the calyx of several species 

 of Apiocrinus given by de Loriol in the Paleont. Franrai.se (Plate -33, Fig. T, 



