268 PROCEEDINGS OF THE ACADEMY OF [1885. 



Crinoids was Prof. Allman. He suggested an analogy between 

 the transition stage of Antedon and the permanent condition of 

 Haplocrinu8 f Coccocrinus, Stephanocrinus and Lageniocrinus. 

 In these genera he took the plates covering the ventral surface 

 to be the orals. We have already shown that the ventral pyra- 

 mid in Haplocrinus and Coccocrinus is composed of interradials 

 and not of orals, and the same ma}' be said of Stephanocrinus ; 

 while the so-called orals in Lageniocrinus are radial in position, 

 and evidently arm pieces. 



The next writer on this subject was Prof. Zittel, who thought 

 these plates were present in Haplocrinus, Coccocrinus, Symbatho- 

 crinus, in the Cyathocrinidse, Hybocrinidse and Crotalocrinidse. 

 That the so-called orals in the Cyathocrinidse and Hybocrinidse are 

 interradials can no longer be doubted ; while the orals of Zittel 

 in Symbathocrinus prove to be merely articular extensions of the 

 radials, which, in their form, somewhat resemble the orals of 

 recent Crinoids. The so-called orals in the Crotalocrinidse are 

 identical with the proximals (nobis), and will be discussed in 

 connection with them. 



De Loriol substantiall}" accepts Zittel's classification, and also 

 his interpretation of the plates. 



Dr. P. H. Carpenter, in the Challenger Report, no longer 

 regards the large interradial plates in the Cyathocrinidse and 

 Blastoidea as orals, but, as before, he applies the term to the 

 interradials of Allagecrinus and Haplocrinus, and to the inner 

 ring of interradials in Coccocrinus. He also designates as orals 

 the six proximals surrounding the central piece, and calls the 

 latter the " orocentral." He further states that orals were 

 "represented in the vault of all Palseocrinoidse, whether simple 

 or complex, although they are sometimes very greatly reduced." 

 Carpenter's views agree essentially with those of Zittel, only that 

 he extends the term to the proximals in all cases, while Zittel 

 applies it exclusively to those of the Crotalocrinidse. According 

 to his description, the vault in the Platycrinidae is paved with 

 well-developed " Centralplatten," and in his general remarks on 

 the Actinocrinidse he speaks of "seven Scheitelplatten," sur- 

 rounded by a greater or smaller number of radial and interradial 

 plates. 



As for ourselves, we have described orals in Haplocrinus, 

 Coccocrinus, and in the Cyathocrinidse; but, as already stated, 



