1887.] NATURAL SCIENCES OF PHILADELPHIA. 105 



serious exceptions if the ventral plates in Allagecriiius, Haploerinus, 

 Culicoci'inus and Coccocrinus, as asserted by Carpenter, represented 

 the orals. We think it was the superficial resemblance in the form 

 and position of these plates with the orals of certain Neocrinoidea 

 that led Carpenter to regard them as orals. He probably overlooked 

 the fact that the plates agree equally well on those points with the 

 interradials of the Cyathocrinidae, and that as interradials the above 

 genera would not be exceptional types, but comply with the morpho- 

 logical conditions of all their contemporaries. 



We have shown that GuUcocrinus and Coccocrinus, as members 

 of the Camarata, should have more than one interradial plate, and 

 it is not very likely that the secondary one, exceptionally in those 

 genera, would be substituted by a ring of oral plates. But there is 

 another serious difficulty. The slits in C bacca extend out to the 

 first row of ventral plates as well as to the second, and this suggests 

 that, if Coccocrinus were "like the recent genus Holopus" to be "per- 

 manently in the condition of a crinoid larva, in which the orals have 

 not yet moved away from the radials, though separated from one 

 another,"* then both rows of plates were orals, one ring within the 

 other. Where among the numerous families of the Palaeocrinoidea 

 do we find an instance in which the plates constituting either the 

 oral pyramid or the proximals, are separated in that manner? 

 Nowhere ; but if there was such a case, we certainly would find it in 

 the highest developed forms and not in the larval ones. Again, where 

 do we meet among Palaeocrinoids with an open peristome? In the 

 earliest stages of the Neocrinoid larva, the orals are closed, and in the 

 earlier forms of the Camarata, such as Reteocrinus, Glyjjtocrinus, etc., 

 the peristome is closed either by the upward growth of the calyx, or by 

 a small central piece, there being no proximals, and hence, accord- 

 ing to Carpenter's interpretation of these plates, no orals. Those 

 genera appear to us to be in a similar condition to Allagecriiius and 

 ifapfocrift(ts among the Inadunata, and Cullcocrinus and Coccocrinus 

 among the Camarata, but not in the condition of the Neocrinoidea at 

 all. However, we can readily understand why Carpenter holds so 

 tenaciously to these plates as orals, for it is principally upon these 

 plates that he bases his further theory, that in the higher Palaeocri- 

 noidea the orals are represented by the proximals ; indeed they are 

 his "simplest forms" which he failed to find among Blastoids. In 

 the Challenger Report on p. 170, he says: "The proximal dome 



*Chall. Report, p. 163. 



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