1895.] MR. F. A. BATHER OK UINTAOBIITUS. 979 



The crown consists of a relatively large, globose calyx and 10 

 long arm-branches (PI. LV.). 



The calyx was flexible, as shown by the thinness of the com- 

 ponent plates, the absence of fractures, and the regularity of the 

 preserved specimens. The dorsal cup alone is known to us. 

 The tegmen was pliable, and probably but slightly, if at all, 

 plated ; at any rate, none of the ventral plates are exposed, 

 " nor," as says Mr. Hill (9), " has it been possible to expose them 

 by dissecting away the plates." Neither does a transverse section 

 of a calyx, at about the level of the 6th fixed distichal, show more 

 than a confused calcareous mass. 



The dorsal cup (see figs. 4 and 5) consists of three categories 

 of elements : (a) the apical system ; {h) the brachial elements, 

 which are radial and primary ; (c) the secondary, supplemental 

 plates, A'iz. (i.) interbrachials, (ii.) interdistichals, (iii.) interpin- 

 nulars. 



The apical system (PL LIV. fig. 1) consists of (i.) the centrale 

 or central apical plate ; (ii.) 5 interradially situate basals sur- 

 rounding it ; (iii.) 5 radials succeeding the basals. 



The centrale is pentagonal, but in specimens examined not 

 quite regular. In specimen e its greatest diameter is 1'5 mm. 

 It is perfectly smooth, showing no signs either of a stem-attach- 

 ment or of partition into more than one original element. Its 

 homologies are therefore doubtful, as its structure and position 

 permit it to represent either a relic of a stem, or a fused infrabasal 

 circlet, or even, as some would have it, an additional element 

 altogether to which the name '* dorsocentral " might be strictly 

 applicable. I have recently ^ given reasons for rejecting the term 

 and the idea " dorsocentral." Which of the other alternatives 

 be correct is to be decided, if at all, by reference to the affinities 

 and origin of the genus, as to which we are, at this stage of the 

 inquiry, quite in the dark. 



The basals (PI. LIV. fig. 1) are 5, equal, regular, and pentagonal. 

 They surround the apical plate and meet each other by adjacent 

 sides. The sides enclosing the upper angle of each basal are 

 sHghtly curved convexly, thus giving the basals a petaloid aspect. 

 The measurements of the basals in specimen e are : height 3'4 mm. ; 

 width below, 1*0 mm. ; width above, 3-5 mm. 



The radials (fig. 5 and PI. LIV. fig. 1) are 5, equal, heptagonal 

 or hexagonal according as the upper sides of the two basals on 

 which each radial rests make a reentrant angle or a straight Hne. 

 They meet each other by adjacent sides, support the first primi- 

 brachs above, and abut on the proximal interbrachials on either 

 side. Their measurements in specimen e are : in one radius, 

 height 5-0 mm. ; width below, 4*9 mm. ; width in middle, 8*7 mm. ; 

 width above, 5-75 mm. : in another radius, height 6-0 mm. ; width 

 below, 4-5 mm. ; width in middle, 8-0 mm. ; width above, 4*5 mm. 



The fixed brachial elements that enter into the composition of 



1 " The Text-book Writer among the Echinoderms," Natural Science, vol. yi. 

 pp. 415-423 (1895). 



