KONGL. SV. VET. AKADEMIKNS IIANDL. P.AND. 19- N:0 7. 63 



a near approach to a calyx of that simple description was to be seen in Cyathocrinus, 

 and one of its species, Cyathocrinus (Poteriocrinus) geometriens Goldf. was therefore 

 selected to open a series of figures \) hj which, — while leaving to others the moro 

 difficult task of unravelling the perplexedly diversified composition of the Crinoidean 

 calyx, ■ — • I endeavoured to exhibit the homologies between the constituents of the 

 calyx in that Palasocrinoid and those of the apical system in typical forms of Echi- 

 noidea. It then appeared that this sj^stem is not an assemblage of parts, each con- 

 trived for the special purpose of subserving the function of an internal organ, one as 

 a temporary appendage of the excretory opening, another as an accessory of the system 

 of aqueous circulation, others as bearers of the organs of vision, and others again as 

 mere holders of the outlets of the sexual organs, but that, in reality, the apical system 

 is by itself an independent Avhole, morphologically equivalent to each of the two other 

 systems, the perisomatic and the ambulacral, constituted of three elements, intimately 

 combined and normally disposed radiately in regard to its centre. And these elements, 

 which are rarely seen simultaneously present in the adult, I ventured to point out as 

 homologous: the central one to the whole of the pentagonal Basis (Joh. Muller) of 

 the Crinoidean calyx; the five ossicles of the proximal set called »genital» in the former, 

 to the Parabasalia (Joh. Muller) in the latter; and the five outermost ossicles in the 

 Echinoid, usually termed »ocellar», to the Radialia (Joh. Muller) of Cyathocrinus. ^) 

 And it was shown that the same homologies hold good in the Asteriadea. 



If this view is well based, as I believe it is, it follows that a terminology has 

 to be found, which ixiay be applied equally in the different classes, and which desi- 

 gnates homologous parts by identical appellations. Now, among the numerous deno- 

 minations proposed by authors, three have been more widely used. The constituents 

 of the calyx are termed 



in Cyathocrinus: by 



Miller: Pelvis. Uostalia. Scapuhie. 



Joh. Muller: Basis. Parabasalia. Radialia. 



Herb. Carpe>,ter: Infrabasalia. Basalia. Radialia; 



in EcHiNOiDEA: by 

 Authors : Central plate. Geuital plates. Ocellar plates. 



The position of the calycinal system, while basal in the Crinoidea, is culminating in 

 the Echinoidea and the Asteriadea, and consequently any appellation involving the 

 notion of a basal position must be avoided. On the other hand, the terms: genital 

 and ocellar, besides being expressive of incidental relations peculiar to the Echinoidea 

 and partly to the Asteriadea, cannot by any means be applied to the homologous parts 

 in the Crinoid. For these reasons, and to avoid multiplying terms already too nume- 

 rous, I proposed to retain the old name of costals Miller — the quaint allusion it 

 implies being long forgotten — for that of parabasals Joh. Muller, and thus to deiine 

 the calycinal system, or the calyx, in the Cyathocrinid», the Echinoidea and Asteriadea, 



') Études, p. 80. — *) Ueber den Ban des Pentacrinus, p. 31. 



