XI. Balanocrinus. 395 



Measurements of cirrus-facets in millimetres : — 



E 21984. E 21982. E. 21978. E 22027. 

 Mean diameter of columnal . . 7"65 



Width of facet 2-0 



Eadial diameter of facet .... 10 

 Distance of axial canal from 



outer margin 10 I'lo 1-2 1"2 



The cirrus-notcli in the hypozygal varies greatly in depth. 

 Sometimes it is a slight almost V-shaped notch in the 

 margin. Sometimes a cliannel^ gradually shallowing, 

 stretches down the radius over two or even three columnals. 

 How far this appearance is due to pressure after burial 

 is uncertain, but it is worth noting that in E 21989 the 

 granular ridge of the hypozygal side-face continues across 

 such a channel. A characteristic form is seen in some well- 

 preserved specimens (e. g., E 22027, tig. 4 ; E 21978) ; as 

 seen from the side it is of roughly four-sided outline, and 

 occupies the upper two-thirds of the side-face ; the shorter 

 vertical sides approach one another slightly as they pass 

 downwards, the up|)er edge is clearly marked, and is sharply 

 bent inwards, corresponding no doubt to the angular inner 

 margin of the formerly apposed cirrus-facet ; the floor is 

 marked with two indentations, one above the other, and 

 presumably corresponding with the first and second cirrals. 

 In E 21989 three such indentations are seen in succession, 

 and the dividing elevations can be distinguished from the 

 continuations of the granular ridges previously mentioned. 



The remains of Cirri are rare. In only one or two cases 

 is a cirral ensconced in the hypozygal notch or lying close 

 by ; in no case is a cirral still attached to the facet. In 

 E 21989 a single cirral lies on the joint-face of the hypo- 

 zygal. Its joint-face is a broad ellipse with one side 

 flattened ; the long diameter is 1*75 mm., the short one is 

 1'3 mm. ; the margin is slightly raised ; the fulcral ridge 

 bisects what would have been the ellipse and passes round 

 the axial canal, widening more to the elliptical boundary 

 of the joint-face. Since on the facet the straight side of 

 the fulcral ridge is the outer side, it may be inferred that 

 the flattened side of the cirral was outermost, and that the 

 curved side rested in the hypozygal notch. The height of 

 this cirral is about "8 mm. Whether the face described is 

 proximal or distal cannot be decided. 



Alternicirration. — The most interesting feature in this 

 species is that diminution in the number of cirii at the 

 ■whorl to which the name diductylus is due. The number 2 



