THE JOUENAL 



OE 



THE LINNEAN SOCIETY. 



On certain Points in the Morphology of the Cystidea. 

 By P. Hebbekt Carpenter, D.Sc, F.E.S., E.L.S., Assistant 

 Master at Eton College. 



[Eead 15tli January, 1891.] 



(Plate I.) 



1. The Body Plates. 



In many Cystideans the plates enclosing the dorsal part of the 

 body are as regularly arranged as in the cup of a Crinoid, and 

 various comparisons have been drawn between the two. Grottsche*, 

 for example, has endearoured to find a correspondence between 

 the calyx of Semicosmites and that of Actinocrinus, which has a 

 hexagonal base consisting of three equal plates. The supposed 

 base of Semicosmites is also hexagonal, but is composed of four 

 plates, two large and two small (Pi. I. fig. 1 ; ih, 1-4). Grottsche 

 supposes that the suture between the two larger ones indicates 

 the position of the anal iaterradius, and he describes the cup as 

 consisting of " 4 B, 5 E', 3 E," (schmal, rechteckig), 5 IE', von 

 denen eiues direct mit der Basis articulirt, und 2 IE" liber diesem 

 unpaaren IE'." 



One great objection to this analysis is that the supposed azygos 



* Sitz.-Ber. Ges. Nat. Freunde Berlin, 1886, p. 13. 

 LINN. JOUEN.-^ZOOLOGV, VOL. XXIY. 1 



