Supposed Absence of Basals in the EugeniacrinidaB. 327 



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I 



XLIL — On the Supposed Absence of Basals in the Eugenia- 

 crinicUe and in certain other Neocrinoids. By P. Herbert 



Carpenter, M.A., Assistant Master at Eton College. 



Although it is well known that the basal plates are of 

 fundamental importance in the morphology of a Crinoid, and 

 are the earliest of the calyx-plates to appear in the larva, yet 

 they are generally supposed to be absent in several members 

 of the order. The oral plates, which appear, together with the 

 basals, shortly after the conclusion of the gastrula-stage, do 

 indeed entirely disappear in the full-grown Pentacrinus and 

 Bathijcrinus and in most Comatidce ; but this is not the case 

 with the basals, either in these genera or in any other living 

 Crinoid. Nevertheless it seems to be thought by some palae- 

 ontologists either that certain Crinoids never had any basal 

 at all, or else that the larval basals undergo a still more com- 

 plete resorption than those of most recent Gomatulca do, and 

 disappear ait< tgether from the calyx of the adult. These plates, 

 however, have such a very definite relation to important 

 internal organs, that their total disappearance seems impro- 

 bable, while there are some reasons for thinking that they 

 are actually present and even well developed in various 

 Crinoids which are supposed to be altogether without them. 



According to Mons. de Loriol* the calyx of the Eugenia- 

 crinidae is composed of radials only, without any basals ; and 

 he considers the absence of basals to be an important character 

 distinguishing this family from the Apiocrinida; and Penta- 

 crinidse. Beyrichf; however, for reasons to be mentioned 

 later, came to the conclusion that the basals of Eugeniacrinus 

 are internal and situated within the ring of radials with which 

 they are united; and ZittelJ supposed, for the same reasons, 

 that rudiments of basals which had perhaps been present in 

 early life are to be found in the adult calyx, though enclosed 

 by the upper part of the radials. De Loriol§, however, has 

 been unable to detect any traces of such internal basals. 

 Beyrieh had previously pointed out that their presence would 

 indicate an affinity between Eugeniacrinus and Rltizocrintis. 

 The calyx of the latter genus, as described by Sars||, consists 



* Crinnules \\ ilei de la Suisse (Geoeta, 1877-79), pp. 196, 197; and 

 also Pal&mtologie Fnmraise: Terrain Jura ique, tome xi. pp. 74, 75. 

 t Zeitschr. d. deutech. geol. GeseUsch, 1869, Bd. xxi. p. 835. 

 X PalflBontologie, Bd i.p. 885. 

 § Pa&ontolo e Francai , loo, clt. p. 77. 

 || M^moiree pour seirir a la cormaisaanc* j Crinoid i vivanta (Chris- 



tiania, l& ), p. 12. 



