282 Bibliographical Notices. 



early forms of exocj'clic Urcliins have the anus placed in or near the 

 calycinal system, from which it gradually recedes in those of later 

 date. May not some change of this kind he traced in the relations 

 of the anus to the actinal system of Palaeocrinoids and Neocrinoids ? 

 In any case, however, this objection about the position of the anus 

 comes rather oddly from critics who regard the undivided central 

 plate of the actinal side in a Palseocrinoid as the "true homologue " 

 of the quinquepartite oral pyramid of a Neocrinoid, and are also 

 candid enough to describe on p. 50 how the anus of the Calyptocrinida9 

 is strictly central, " while the central piece is bisected, and the two 

 halves, jointly with the proximals, form the sides of the anal tube." 



The authors make the same objection to the view of Allman, 

 Wyville Thomson, Dr. Carpenter, and most later writers that the 

 ventral pyramid of Haplocrinus consists of five united oral plates ; 

 for they repeatedly state that one of these five large plates which 

 they call interradials is pierced by the anal opening, and their figure 

 on plate v. shows an exceedingly minute puncture at its central end. 



We do not say that this is not an anal opening ; but, considering 

 the length of time that Haploci'inus mespiUformis has been known 

 and the many writers who have figured and described it without 

 noticing this point, we cannot but think that further evidence is 

 necessary. Neither anal opening nor central piece are visible in 

 Hall's figures of Haplocrinus clio, nor have we been able to find 

 them in the British species of the genus. 



The authors take the same view of the five plates covering the 

 mouth of Stephanocrinus and Allagecrinus as they do in the case of 

 Haplocriyius, regarding them not as orals but as calyx-interradials. 

 But these plates appear to us in all three genera to be truly 

 homologous with the orals of the Pentacrinoid larva. They cover 

 the mouth and the origins of the ambulacra, just as the orals do in 

 the young Neocrinoid, and this relation is not characteristic of the 

 primary calyx-interradials in any other Crinoid. The converse of 

 the above argument is employed by Messrs. Wachsmuth and Springer 

 on p. 22 to disprove the " oral " nature of the interradials in Ct/atho- 

 crinus. That these plates " are interradials, and not orals, is proved 

 by the fact that they surround the peristome but do not cover it, 

 and are succeeded by numerous other plates " (i. e. if they covered 

 the peristome Wachsmuth and Springer would call them orals). 

 But nevertheless the five plates which do cover the peristome in 

 Stephanocrinus, AUaffecrinus, and Haplocrinus are regarded by these 

 authors as calyx-interradials. 



It is only in the Cyathocrinidae and in the Blastoids that the 

 interradials have any close relation to the mouth at all ; but they 

 do not cover it in and shut it off completely from the exterior as 

 the dome-plates of StepJianocriyius and Allagecrinus do, for they 

 form the circumference of the peristome from which the ambu- 

 lacra pass outwards over their apposed lateral edges. There is 

 not a single Crinoid known in which plates that are universally 

 recognized as calyx-interradials cover in the actinal centre. 

 The very name " calyx-interradials " implies plates that are 

 abactinal in their origin ; while in Palaeocrinoids, Blastoids, and 

 Cystids alike we meet with types, such as Allagecrinus, Stepha- 



