46 CALAMOCEINUS DIOMED.E. 



to 14 of Plate IX. with Figure 8, a, b, c, which represent corresponding side 

 plates. The oral plate varies also in Figures 8 and 9. The upper end of 

 the oral is somewhat askew, and hence the profile (Fig. 11) seems more 

 different than it really is from that of the corresponding profile (Fig. 9). 

 Figure 7 is drawn somewhat obliquely to show the difference in the two 

 sides of the oral plate, o, on the upper extremity above the central 

 keel, o'. 



Stem. 



The stems of the three specimens show very considerable differences, 

 and the different parts of the same also vary greatly in their physiognomy. 

 In the upper part of the stem the rings vary very materially, from being 

 quite smooth (Plate XVIII. Fig. 1) to being strengthened by a strong 

 central ridge (Plate XVII. Fig. 1). In the latter case we have serrated 

 sutures, while in the former stage they are smooth. In another specimen 

 the upper joints combine the characteristics of the other two. The}' are 

 smooth, with smooth sutiu'es, passing from rings with smooth sutures and 

 small imperceptible tubercules (Plate XVII. Fig. 10) along the median line 

 to rings with connected tubercular ridges with smooth sutures on the ridges, 

 and lower down along tlie stem to rings with serrated sutures and marked 

 central ridges (Plate XVII. Figs. 8, 11). 



In the specimen shown in Figure 2 of Plate XVIII., the smooth rings 

 pass directly into rings with slight ridges and somewhat irregularly and 

 indefinitely serrated sutures, and these pass gradually into rings with more 

 finely serrated sutures and with less and less distinct median transverse 

 ridges (Figs. 4'', 5'), until they pass again into regularly discoidal rings 

 with smooth sutures (Fig. G**) ; and it is rings of this character, but more 

 flattened (Fig. 9), such as are figured from another fragment of a stem, 

 which continue to the very base of the stem, at the same time slightly 

 expanding in width towards the base, much as they have been figured for 

 the fossil species of Apiocrinus and Millericrinus. The upper rings of the 

 stem adjoining the calj'x expand slightly, and pass as it were into the 

 outline of the calyx (Plate XVII. Figs. 1, 8, 9, 10, Plate XVIII. Fig. 1). 

 But this expansion of the basal rings of the stem does not compare with 

 the extreme condition which is reached in the fossil Apiocrinus, in which 

 the upper joints form a part of the cup outline of the calj^x. 



In those parts of the stem intervening between the lower portion nearer 



