222 Reviews — Wachsmuth and Springer — On Crinoids. 



are covered by perisome," and because in the posterior interradius 

 they do not rest on the special anal plate. They now believe that 

 " the perforated plate is a true anambulacral plate, analogous with 

 the perforated limestone particles at the disk of recent Crinoids," 

 and that the two narrow plates and " possibly also the four larger 

 ones, wholly or in part, are subambulacral plates." 



This view is absolutely new and, if proved, of great importance ; 

 its adequate discussion is beyond the limits of a review, but we 

 cannot refrain from a few remarks. "What do the authors mean by 

 "subambulacral plates"? The term was proposed by Joh. Miiller 

 in 1854 for a series of median plates lying beneath the food-groove 

 of Fentacrimis asteria, and therefore radial in position like the 

 lancet-plates of the Blastoids. But the plates now under discussion 

 are interradial in position, and only their edges are immediately 

 beneath the food-groove. This difficulty must have been seen by 

 the authors themselves, for they say : " interradial plates, as the 

 term denotes, cannot be suhambulacral." It is hard to see how 

 they better their position by the suggestion that these plates are 

 homologous with the deltoids of Blastoidea, and that they each 

 consist of a median interradial plate fused with two lateral plates 

 that underlie the ambulacra. Not only is this, as they admit, 

 unsubstantiated hypothesis, but if proven, while it would leave an 

 interradial portion still to be accounted for, would not make the 

 lateral portions one whit the more subambulacral, although they 

 might then be considered as adambulacral. 



We do not here wish to maintain that the plates are orals, but 

 the authors hardly seem to have given good reasons for the rejection 

 of that view. How do they know that ambulaci-a cannot pass over 

 the edges of orals ? The change may have taken place gradually, 

 and is no more impossible than the sinking of ambulacra. They 

 must show both orals and these interradial plates coexisting in some 

 particular specimen ; and this they do appear to state on p. 357 : 

 " That the plates are not orals is further proved by the fact that 

 there are in Cyathocrinus iowensis other large plates covering the 

 peristome, which naturally represent them." But they do not say 

 how they distinguish the partly resorbed orals from the large 

 covering plates that, in the same specimen (pi. x. fig. 3), are stated 

 to join in the centre. 



Then again the plates are stated not to be interradials, because 

 they are covered by perisome ; but have the authors ever seen a 

 specimen in which these plates existed but were entirely hidden by 

 interambulacral plates ? If so, it would have been well to have 

 definitely stated as much ; and even then, why should not an 

 interradial plate sink below others until it is covered by them ? 



Some argument, which we do not follow, is based on the " per- 

 forated " plate or " madreporite." Now this plate has been known 

 for some time, and presents all stages of folding, rugosity, and 

 pitting, but that the pits represent pores rests on the statement of 

 these authors. It is a pity that, with their abundant material, 

 they did not cut a single section so as to prove the point. This 



