1074 NOTES ON AUSTRALIAN FOSSILS, 



To accompany this I give a revised figure of the diagram, and a 

 correct sketch of one of the radials with probably ankylosed 

 brachials as suggested by the authors of the Revision. (1) 

 (PI. XVI, figs. 3 &4.) 



The suggestion that the two radials symmetrically disposed are 

 " compound plates, each representing a radial and a bifurcating 

 brachial, which probably became ankylosed," (2) seems to me 

 perfectly acceptable, but although I am not ready to discuss the 

 opinions of, no doubt, the best authorities on crinoids, I may perhaps 

 remark that the ankylosed brachials are very much reduced in size 

 and thickness, and that, if, according to Messrs. Wachsmuth and 

 Springer, "they evidently supported two arms, one at each side," 

 these arms were probably abortive, or at any rate very much 

 reduced, or reduced next to nothing, as I do not see any sockets 

 for them, nor any strength to support them. This does not at all 

 mean that the plates in question were not brachials, but that they 

 probably became ankylosed through having lost their functions. 



At p. 1163 (I.e.) I have spoken of small covering plates repre- 

 sented in plate 68, figs. 2 and 3. They are no doubt plates, 

 as their impression appears distinctly on the outer as well as on the 

 inner cast. In my paper, comparing these plates with those of the 

 flattened vault in Rhodocrinus as represented in de Koninck's 

 work, I took them to be vault plates. But, according to 

 Wachsmuth and Springer (3) "if they are plates at all, they 

 formed a part of the disk, and as such were covering pieces " — I 

 cannot follow the authors in the study of pieces which are rarely 

 observed in specimens of common occurrence, although of great 

 importance in the classification. For this reason, and in consequence 

 of the complicated arrangement of these pieces, the evidences given 

 by previous writers are very confusing, and light is thrown upon 

 the subject in Part III. of the l Revision ' in the chapter treating 



(1) Revision, Part III. Sect. 2, pp. 174, 175, and plate VI. fig. 5. 



(2) Revision, Part III. Sect. 2, p. 174. 



(3) Revision, Part III. Sect. 2, p. 174. 



