CALAMOCEINUS DIOMED.E. 51 



end is 4.9 mm., and of the small end 4 mm. At the upper part of the 

 stem the joints are alternately smooth and ridged (Fig. 3), until at the 

 lower third of the stem the smooth joints show indications of a slight 

 ridge (Fig. 4), and gradually all the joints become ridged (Fig. 5). 



Another piece (Plate XVIII. Figs. 7, 8) is very slightly curved towards 

 the stouter end, 135 mm. long, 5 mm. in diameter at the large end, and 

 4 mm. at the smaller end. There are seventeen joints to 20 mm. both 

 at the smaller and at the larger end ; the articulations of both Figures 

 7 and 8 are very smooth and very distinct. 



A piece 150 mm. in length (Plate XV^II. Figs. 12, 13) is slightly curved 

 in the middle, 4 mm. in diameter at the smaller end, and 4.1 mm. at the 

 larger end. There are seventeen joints to 20 mm. at the larger end, and 

 eighteen joints to 20 mm. at the smaller end. The articulations are like 

 those of Fio-ure 14. 



A piece of stem, 130 mm. long, practically straight, has at the smaller 

 end nineteen joints to 20 mm., and seventeen joints to 20 mm. at the upper 

 end. The diameter is 4.4 mm. at the smaller end, and 5.25 mm. at the 

 larger end. It resembles Plate XVIII. Figs. 7, 8. 



One piece, 115 mm. long, is slightly curved. The diameter is 3.7 mm. at 

 the small end, and 4 mm. at the other. It has fourteen joints to 20 mm. 

 at the small end, and fifteen joints to 20 mm. at the large end. The joints 

 are smooth and sharply ridged, giving a zigzag outline to the edge of the 

 column, somewhat as in Plate XVII. Fig. 12. 



The Top Stem Joint. 



The top stem joint (Plate XXI. Fig. 1) is slightly arched from the outer 

 edge towards the central portion of the joint, which is somewhat sunken 

 to receive the quinquelobular new young joint (Plate XXI. Figure 3), which 

 occupies a part of the space intervening between the upper surface of the 

 top stem joint and the lower fixce of the basal ring (Plate XTX. Fig. 1). 



The upper face of the top stem joint is finely striated from the outer 

 edge inward, and shows a series of irregular radiating slightly raised angular 

 ridges, similar to those figured by D'Orbigny and de Loriol on the upper 

 face of the ariicle basal of the Apiocrinida?. Towards the median part of 

 the surface of the joint the reticulation becomes cellular, losing its radiat- 

 ing arrangement, and gradually passes from a comparatively close and 



