Bibliographical Notices. 283 



nocrinus, and Glyptosphcerites, in which the mouth is covered by 

 a pyramid of five closely fitting plates as in Neocrinoids {Hyo- 

 crinus), Urchins (Palceostoma), and Holothurians (Psolus). There 

 is therefore very strong evidence for regarding all these plates 

 which have the same relations in five different classes of Echino- 

 derms, and also occur in Asterids and Ophiurids, as mutually 

 homologous, i. e. as oral plates. The very fact that actinal plates 

 homologous with the basals of the abactinal side occur in every 

 group of Echinoderms is sufficient to show their primary morpho- 

 logical importance ; and it is not altogether in accordance with 

 Wachsmuth and Springer's statement on p. 32, that " the phylo- 

 genetic evidence indicates clearly that the interradial element takes 

 a most prominent part in the composition of the Palaeocrinoidea ; " 

 and again, *' Upon palseontological grounds we expect to find in the 

 younger stages of the Palaeocrinoid the oral system feebly, the 

 interradial system extravagantly developed, while, according to 

 Carpenter's interpretation of the plates, in the Palaeocrinoid larva, 

 the entire ventral surface from the radials up would be oral, i. e. 

 actinal." This is precisely what we believe to be the case in larval 

 forms like Haplocrinus and Allagecrinus. 



The authors ask on p. 32 whether it is probable that these two 

 genera " alone among all Palseocrinoidea should have no interradial 

 plates ?" To this we reply, " Certainly not ; " for we know on the 

 very best authority {i. e. their own) that interradials are " entirely 

 absent " in some genera of the Ichthyocrinidie ; " while there are still 

 other genera and certain species in which they are occasionally 

 undeveloped dorsally." These remarks about the interradials occur 

 on p. 19 ; and yet we are told, on p. 73, that " according to our in- 

 terpretation they are present in all Palaeocrinoids," and that they 

 are " well-defined and permanent plates !" 



On the same page is the following remarkable statement : — 

 " Carpenter denies that interradials are present as a rule in Palaeo- 

 zic(!) Crinoids, and he therefore does not attach to these plates the 

 value which we think they deserve." No authoritative reference is 

 given for tliis assertion, and the writer has certainly never made an 

 explicit denial of this kind. On the contrary, he has said that 

 calyx-interradials are '' very usually present," or present in " most " 

 Palaeocrinoids : though he is by no means prepared to admit that 

 they occur in either Hajilocrinus or Allagecrinus, as Wachsmuth and 

 Springer assert. 



He must further emphatically protest against the kind of argu- 

 ment which is employed by these authors to demonstrate the truth 

 of their views respecting the summit of Allagecrhms. The following 

 passage occurs in the description of this structure by Mr. Pi.. Ethe- 

 ridge, Jun., and the writer, which appeared on p. 2SG of the 

 ' Annals ' for April 1881 : — " In none of these small specimens is 

 there any trace of an anal opening, either directly piercing an oral 

 plate or at the margin of the dome, between the orals and radials. 

 The central end of one or more of the former may he marTced hy 

 faint tubercles (figs. 5 & 7, pi. xvi.) ; but we cannot suggest any 

 explanation of these." 



On p. .33 Messrs. Wachsmuth and Springer put the words which 



