Mr. ¥. A. Bather on British Fossil Crinoids. 323 



from an arm. As to the homologies with Antedon-lavva, 

 they differ from P. H. Carpenter, for they write : " The 

 different phases in the Paleontological development of the 



azygous side resemble most remarkably the stages 



of growth in the anal arrangement of Antedon .... At a 

 time when even the radials were yet imperfectly developed, 

 we find in both forms a large anal (azygous) plate (Baero- 

 crinus), which is lifted out from between the radials [Hijho- 

 crinus) and becomes developed into a conspicuous funnel (the 

 later Cyathocrinidae), until at ihe termination of Pentacrinoid 

 life and the close of the Carboniferous, the anal plate disap- 

 pears entirely [Erisocritius (39)]." "... The ' anal ' plate 



of the young Antedon is not the homologue of the 



'special' anal plate [x], but of the undivided 



azygous plate in Baerocrinus and Iloplocrinus [Az] 



The special anal plate in llybocrinus is the first step towards 

 a plated tube." 



In 1885 Messrs. Wachsmuth and Springer [Rev. III. 

 Section 1 (11, 12, & 40), Proc. 1885, pp. 233, 231 & 262] 

 substantially repeat their 1883 hypothesis, with, however, the 

 following important additions and alterations. The lower 

 segments of the compound radials, where such occur, were 

 probably embryonal plates (/. e. of an ancestral character), 

 which were absorbed by the upper segments or permanent 

 radials in the same way as the " azygos " and " anal " plates 

 were absorbed by the right posterior radial. The " azygos" 

 piece may indeed itself represent one of these lower segments, 

 viz., that of the right posterior radial ; this is well seen in 

 Anomalocrinus (PI. XIV. fig. 8) and Ectenocrimis (PI. XIV. 

 fig. 7). This very slight admission does not really alter 

 their previous view that the azygos plate was a primitive 

 fundamental element of the dorsal cup ; for what they give 

 with the one hand they take away with the other, in that 

 they make all the lower radial segments similar primitive 

 elements. The anal plate ( x ) and the right posterior radial 

 are as before supposed to be derived from the azygos. But 

 they change their ideas as to the " anal " of Antedon-larva.. 

 The azygos plate, they now say, is unrepresented in the 

 Pentacrinoid ; this is odd, but perhaps it has been over- 

 looked. 



In 1886 Messrs. Wachsmuth and Springer re-enforce these 

 views. [Rev. III. Section 2 (196 & 199), Proc. 1886, 

 pp. 120 & 123.] The "anal" of AntedonAarva is an 

 interradial with special function, while the azygos plate is as 

 much radial as interradial. " They both agree, however in 

 being absorbed by other plates ; the azygous plate pala3onto- 



