REPORT ON THE CRINOIDEA. 75 



fig. 7a), a character which presents itself in Antedon carinata (PI. III. fig. la) and in 

 Antedon macronema (PI. IV. fig. 3a), and is more especially distinctive of the genus 

 Actinometra, in which the muscle-plates, well marked in Eudiocrinus, are very much 

 reduced in size (PI. V. figs. 1-5, b). 



The special peculiarity of the calyx in Eudiocrinus semperi, however, is the way in 

 which the muscle-plates stand up above the sides of the radials, owing to their edges 

 being strongly folded in towards the central articular ridge which separates them 

 (PI. III. figs. 7a, 7c). In many species of Antedon the articular facets of adjacent 

 radials are in close contact along the whole length of their sides, as for example in 

 Antedon eschrichti (PL I. fig. 8a), Antedon basicurva (PI. II. fig. 2a), and Antedon 

 breviradia (PL III. fig. 4b). But in other cases the ventral edges of the muscle-plates 

 are more or less folded outwards from the centre of the calyx, so that its interradial 

 angles are marked by five notches, which lie at the upper ends of the sutures between 

 the radials as in Antedon antarctica (PL I. figs. 6a, 6b), Antedon incisa and Antedon 

 angusticalyx (PL II. figs, la, Id, 4a, Ad), the young Antedon breviradia and Antedon 

 quinquecostata (PL III. figs. 5a, 5c, 6c, 6d). But in Eudiocrinus semperi this notch 

 is continued down to the dorsal surface of the radials as a wide groove between the 

 everted muscle-plates of every two adjacent radials (PL III. figs. 7a, 7c) ; so that in a 

 dorsal view of the calyx (PL III. fig. 7b) its interradial angles are not sharp but deejay 

 incised. An indication of the same character appears in Antedon quinquecostata (PL III. 

 fig. 6b) ; but on the other hand the young calyx of Antedon breviradia, which has the 

 ventral edges of its muscle-plates strongly folded outwards (PL III. figs. 5a, 5c), pre- 

 sents a very sharply pentagonal outline in dorsal view (PL III. fig. 56). The same is 

 the case in Antedon carinata, which has rather markedly everted muscle-plates (PL III. 

 figs, la, lc, id); while on the other hand Antedon incisa, in which this latter character 

 is less evident, has slight notches at the interradial angles of the dorsal surface of the 

 radials (PL II. figs. la, lc, Id). The Eudiocrinus-c&lyx, therefore, presents no characters 

 which do not occur in some one or other of the many species of Antedon; but they are 

 all considerably exaggerated, and are combined together in a somewhat unusual manner. 



The interradial sutures on the dorsal surface of the radials are marked by slight 

 grooves, and there are corresponding grooves on the upper face of the centro-dorsal. But 

 they do not appear to have been occupied by any tertiary basals in the form of a star 

 (PL III. fig. 7b). The rosette is tolerably distinct, with a large central opening and well 

 marked radial spouts. But the interradial processes are scarcely visible, so that there 

 appear to be only five openings, one at the inner end of each interradial suture (PL III. 

 fig. 76). 



The calyx of the fossil species of Eudiocrinus {Eudiocrinus hyselyi) like that of 

 nearly all the secondary species of Antedon and Actinometra, is of a very generalised 

 type ; and, but for the discovery of specimens with the arms attached, it would have 



