38 CALAMOCEINUS BIOMYDM. 



radial plates from that given by D'Orbigny* of the same species. They 

 form a continuous pavement of stout plates, intercalated between the ra- 

 dials and extending to the third bi-achial, arranged in two rows and closely 

 fitted between the plates they unite. 



De Loriol also shows that the interradials of Apiocrinus Parkinsoni (Pal. 

 Fran^., XI., Plate 30, fig. P") were perhaps arranged similarly to those of 

 Guettardicrinus dilatatus. While his figures of the interradials of Apio- 

 crinus Roissyanus (Pal. Franc., Plates 41-45) agree essentially with those of 

 D'Orbigny, they are numerous and very unequally developed, varying in 

 number and arrangement in each interradial space. He also figures inter- 

 radials in Apiocrinus magnificus (Pal. Frany., Plate 48, Fig. 1, Plate 49, 

 Fig. 1), where they are very small; in Apiocrinus Cottaldi (Pal. Franc., Plate 

 48, Fig. 26), whicli probably possessed others also ; in Apiocrinus Rathieri, 

 with its large interradial areas (Pal. Fran^., Plate 49, Fig. 2, Plate 50, 

 Figs. 1, 2, 2% 3) ; and in Apiocrinus Murchisonianus (Pal. Franf., Plate 

 53, Fig. 1); he also speaks of them in A. Belthemieuxi (Pal. Fran^., p. 

 313). In the genus Millericrinus he figures interradials in M. Goldfussi 

 (Pal. Franc;'., Plate 93, Figs. 1", 1'') ; in all of which the interradials are 

 characterized by their massive structure and their close fitting to the 

 adjoining radials or brachials, forming as much a part of the calyx as 

 either the basals or the first radials. But there is nothing, as he says, 

 in spite of their massiveness and the variety found in their dimensions or 

 shape, to indicate any differences in the various interradial spaces such as 

 would denote an anal area, as in Palseocrinoids. 



The series of interradials in the fossil Apiocrinidce usuallj' begins with 

 a single plate, irregularly hexagonal, generally larger or very much larger 

 even than any of the other interradial plates. Sometimes, but rarely, the 

 second piece passes alongside of the first. They gradually diminish in size, 

 and, becoming smaller and smaller towards the perisome, form a vault over 

 the ventral surface where the plates may have only formed the support 

 of a thin membrane. 



In speaking of the interradials of A. Parkinsoni, de Loriol states that 

 the interradial pieces, owing to their cuneiform shape, do not always 

 reach the external surface of the calyx, and thus some of the interradial 

 spaces may appear to have no interradial plates, others four or five. 



* As de Loriol suggests, the sutures of the upper interradials probably escaped D'Orbigny's atten- 

 tion, as dc Loriol examined and figured D'Orbigny's original. 



