Structure o/* Crotalocrlnus. 401 



figures further prove that the ventral covering was pliable, or the 

 arms could not have assumed that horizontal position and be folded 

 in other specimens." 



It is unfortunate that of the five figures referred to in the 

 first sentence of the above passage only one is quoted cor- 

 rectly, viz. tab. XXV. fig. 15. The last figure on this plate is 20, 

 and I am therefore at a loss to know which one is meant by 

 pi. 25, fig. 25. Figs. 6 and 7 on tab. vi. represent Eucrinus 

 interradialis and E. ornatus^ and I strongly suspect that, as 

 in the previous case, tab. viii. is the one to which the autliors 

 meant to refer ; while Taf. viii. fig. 10 would have been a more 

 correct citation of the figure of Crotalocrmus jpulcher in 

 Miiller's memoir, " Ueberden Bau der Echinodermen," which 

 is only illustrated by nine and not by thirteen plates. 



It is to this latter figure and to fig. 15 on tab. xxv. of 

 Angelin's work that I now wish to direct attention ; for they 

 are the two on which Wachsmuth and Springer especially 

 rely as proving that the calyx-interradials of CrotalocrinuSy 

 which are so slightly developed on the dorsal side, not only 

 cover the oral pole, but also extend out on to the free rays and 

 roof in the ambulacral covering plates on their ventral side*. 



Most unfortunately, however, for the theory of the Ameri- 

 can authors, the figures in question represent dorsal and not 

 ventral views of the " free rays," and their supposed " pliable 

 ventral covering" formed of interradial plates consists of nothing 

 but the arm-joints themselves. These are seen in their dorsal 

 aspect at one end of Angelin's figure (which I have copied), 

 but are removed elsewhere. This fact is fully explained by 

 the three authors whom Wachsmuth and Springer quote, viz. 

 Miiller, Angelin, and Zittel ; and it can only have been due 

 to some extraordinary oversight on the part of the American 

 writers that they allowed it to escape their notice. The 

 result is an attempt to support their theory respecting the 

 interradials of the Palaeocrinoids by describing the antiamhu- 

 lacral arVn-joints, which are nothing if not radial^ as supers 

 ambulacral interradials ! But this theory breaks down alto- 

 gether, so far as Grotalocrinus is concerned, when tested by 

 facts. 



Thus, for example, Miiller says of his Taf. viii. fig. 10, 

 " Strahlen der Hand, an welchen die Korper der Glieder zum 

 Theil abgebrochen sind, so dass die kleinen Tafelchen an der 

 Bauchseite der Glieder sichtbar sind." 



In like manner Angelin, whose figure I have copied (see 

 p. 402), explained it as follows: — "Squamulas tessellatce ambu- 



* Compare also the description of the " interradials " in the generic 

 diagnosis of Crotalocrmus on p. 149 of the ' Revision,' part iii. 



