IN THE MOEPHOLOGT OF THE CTSTIDEA. 9 



A similar correction should, I believe, be made in tbe descrip- 

 tion of Lepadocrinus, as given by Hall*. He states tbat tbere 

 are four plates in tbe first and five in tbe second series, but only- 

 four in tbe tbird, Wos. 10, 11, 12, 13, tbe last two bearing pecti- 

 nated spaces. Above tbese come tbe five supra-ovarian plates, 

 Nos. 14-18. There is no mention of any additional plate, though 

 19 are shovs^n in bis figure f, which I have copied for comparison 

 vpith tbat of Ecliinoencrinus (PI. I. figs. 3, 6). As in the case 

 of Apiocrinus elegans, it will, I think, be clear tbat tbe supra- 

 ovarian plate which arches over tbe anus is No. 13, or radial D, 

 while tbe rbombiferous plate to its right is really 14, and not 13 

 as believed by Hall. The interradial plate above this, which bears 

 tbe other half of its rhomb, would then be 15, and the corre- 

 sponding one on the left side 18, as I have marked in my copy 

 of Hall's figure (PI. I. fig. 6). 



If this interpretation of tbe calyx be correct, Apiocystis elegans 

 and Lepadocrinus Gehhardi resemble both Ecliinoencrinus and 

 one another in having a complete series of five interradials, 

 making a total of nineteen plates, with pore-rhombs on 1-5, 12-18, 

 and 14-15. The two American species have four ambulacra, a 

 point in which they resemble the British Apiocystis pentre- 

 mitoides, with a similar arrangement of pore-rhombs. But it is 

 not clear whether this last type has all five interradials, and tbe 

 same may be said of the two quadrifasciate species of Pseudocrinus. 

 Hall X 3iid Zittel § have included Lepadocrinus, Pseudocrinus, 

 and Apiocystis under tbe one generic name Lepadocrinus, but it 

 appears to me tbat the two bifasciate species of Pseudocrinus 

 represent a distinct generic type for which Pearce's name should 

 be retained. It is possible that tbe quadrifasciate species and also 

 Apiocystis pentremitoides are congeneric with A. elegans and 

 Lepadocrinus ; but if it should ever be proved tbat tbe inter- 

 radial CD is absent in tbe former and present in tbe latter, 

 Porbes's genus might perhaps be retained, and increased by tbe 

 addition of the two quadrifasciate species of Pseudocrinus. 



The relations of these three genera w^ould then be somewhat 

 as follows : — 



* ' PalEeontology of New York,' vol. iii. p. 127. 

 t Ibid. pi. vii. fig, 23. X Ibid. vol. iii. p. 126. 



§ ' Palseontologie,' Ed. i. p. 421. 



