BASAL PLATES IN CRINOIDEA CAMERATA 



493 



the larger plates would produce six plates instead of five. This difficulty, 

 however, is overcome if we consider that the introduction of the anal plate 

 into the ring of radials necessitated corresponding modifications among the 

 basals, as otherwise these plates would lose their interradial position. It 



inidas (yunng) 



ApFocrihid:e faduli J 



Fig. i. — Diagrams illustrating the evolution of the basals and infrabasals: all 

 figures represent the anal side at the top; c = posterior basal; b and e = postero-lateral 

 basals; c and d = anterior basals; /, g, k, i, k = infrabasals. 



required either the introduction of a basi-anal plate, or an increase in the size 

 of the original pieces. That the latter occurred among the Camerata is clearly 

 shown by the diagrams, and the evidence leaves no doubt at what part of the 

 base the extra width was inserted. 



