Vol. 54. J ME. F. A. BATHER ON PETALOCRINUS. 409 



of the radial facet is exposed in no specimen, and its nature must 

 be inferred from the facet of the arm-fan ; it is safe to say that it 

 was pierced by the axial canal. 



The Teg men is not clearly visible in any specimen. The cup 

 of a is tilted slightly on one side, so that one can look a little under- 

 neath. Despite Mr. Weller's statement, ' No interradials observed 

 on the dorsal aspect of the calyx,' there is seen in interradii i-ii 

 and ii-iii a pronounced plate, just at the level of the arms and 

 passing up on to the tegmen (PI. XXVI, fig. 43). The wax 

 squeeze taken from the impres- -^. o t^- 



sion of the tegmen in f 1 ^^g- ^-—Diagram of the tegmen 

 (PI. XXVI, fig. 45 & text-fig. 3) ^/ Petalocrinus mirabihs to 



shows that the first primibrachs explain PI. XXfI,fig. J^5. 



abut on five radially-disposed 

 plates. These, which are pro- 

 bably radials, project, in a slight 

 angle, to the middle line of the 

 primibrachs, but their inner, 

 adoral margins are straight. 

 They abut on one another by 

 short sides. Therefore in this 

 view they appear pentagonal. 

 Between the radials and the oral 

 centre, but interradially disposed, 

 are subtriangular plates, probably ^^ peristome ; v.g, ventral groore ; 

 one in each iuterradius, with their A, deltoid ; E, radial; IBr, first 



,. ,, . , T 1 primibracli. 



apices meeting the mterradial 



sutures. These plates are interambulacral and are the same as the 

 interradial plates seen in a. They may be homologized with the 

 five subtriangular plates of the Cyathocrinoid tegmen, which have 

 been spoken of in my papers as deltoids, and which, in opposition 

 to P. H. Carpenter and Messrs. Wachsmuth & Springer, I believe 

 to represent orals.^ The other smaller plates of the tegmen are 

 probably ambulacrals, but their arrangement cannot well be dis- 

 tinguished. The wax squeeze seems to show one or two traces of 

 grooves, leading from the brachials, across the supposed radials, to 

 a pronounced but narrow depression in the centre. This latter is 

 no doubt the peristome, and, in the animal, may have been covered 

 by plates ; one cannot infer otherwise from the peculiar state of 

 preservation of the fossil. The anus is not to be detected. 



Mr. Weller, in his paper, spoke of ' the anal side.' In reply to 

 a question, he wrote on May 5th, 1896 : — ' My only reason .... 

 was the apparent slightly greater width between the two arm-bases 

 and the slightly larger basal plate on the same side.' This refers, 

 as he explained by a diagram, to that interradius on specimen a 

 here marked iii-iv. Were this a constant feature, Mr. Weller's 



^ See especially ' Suggested Terms in Crinoid Morphology,' Ann. Mag. Nat. 

 Hist. ser. 6, vol. ix (1892) p. 63 ; ' Brit. Foss. Crin. — VIII : Cyatliocrimis' ibid. 

 p. 225 ; and * Orinoidea of Gotland : I,' 1893, on p. Ill and elsewhere. 



