MOEPHOLOGICAL PART. 



141 



organ is lodged within the centrodorsal, and is covered by the rosette,* it is 

 in rentacrinus, which has no centrodorsal, contained in a cavity formed by 

 the radials above and the basals below. The five chambers of Fentacrinus 

 are not closed at the bottom, but are continued down the stem as five vessels, 

 systematically arranged around a central axis. These vessels were regarded 



Fig. 3. 



Fig 4. 



Fig. 5. 



Fig. 3, position of the axial cords in the yoimg Antedon rosaceus (after W. B. Carpenter) ; Fig. 4, 

 their position in the adult (after A. M. Marshall) ; Fig. 5, in Encrinus liliiformis (after Beyrich). 



cd = centrodorsal ; i = infrabasals ; b = basals ; R = radials. The dark lines show the arrangement 

 of the canals in the dorsal cnp. 



by Dr. P. H. Carpenter as homologous with the five openings around a single 

 one on the underside of the calyx, and along the stem of Ciipressocrinus, Myr- 

 tilocTimis, and Gasterocoma. Among recent Stalked Crinoids a chambered 



* In most of the Comatulae, the embryonic basals are metamorphosed into the structure known as the 

 *' rosette," which is enclosed within the radial pentagon, so as to be not visible externally. 



