42 STRUCTURE OF THE CYSTIDE^. 



arms immediately subdivide again. From the oral aperture 

 grooves beset with marginal plates, pass on to the arms. For 

 the rest, the division of the arms shows that they are arms, and 

 not pinnulce. Whether these arms, like those of a few other 

 Cystideans, as Pseudocrinites, were provided with articulated pinnulse, 

 cannot be decided, since they are broken short off. Whether the 

 Carijocistites possessed arms is not as yet known, but it can hardly 

 be doubted, since they are not certainly distinguishable from 

 Echinosph cerites . 



"In Hemicosmites three of the six uppermost plates of the calyx 

 are provided with an insection, which arises from the tri-radiate 

 median calycine opening. Each of the insections is continued 

 into a groove ; the groove terminates after a slight expansion in 

 an elevation of the calyx which served for the attachment of an 

 arm. The elevation no longer lies on the plates of the uppermost, 

 but upon three of the plates of the second series. The elevation 

 exists only in specimens which are not worn down, and is beautifully 

 obvious in a specimen which M. Ewald has sent me. The tri-radiate 

 clefts of the calyx, and the calycine grooves continued from them, 

 are covered with minute plates which readily fall off*. In the 

 specimens figured by L. Von Buch, they are still perfect, and form 

 a fine series of plates from the mouth to the ventral surface of 

 the three arms. In this series again, three delicate grooves are 

 distinguishable, as in Echinosijhoerites aurantium, which correspond 

 with the subjacent clefts of the large plates of the calyx and 

 their grooves. In the always much worn specimen of Cnjptocrinites 

 cerastis, no indications of arms have hitherto been observed. 



"Forbes regards the Cystidece, like the Blastoidea, as sections of 

 the Echinoderms different from the Crinoids. The SpJiceronkes were 

 already arranged among the Crinoids by reason of their stalks 

 before their arms were discovered, and we now have still more 

 reason for considering this to be their true position. Volborth 

 and Roemer consider the CysiidecB as a group of Crinoids, which 

 is also my own view. The position of the the arms however, 

 must not be regarded as one of their characters ; for in Sphmronites 

 Leuchtenhergii and Protocrinites oviformis the arms were situated 

 far away from the mouth, as in the other Crinoids. 



"The suctorial feet of the Cystideans were unquestionably placed 

 as in Pentacrinus, on the ambulacral side of the arms and in the 

 ealycine grooves. In the introductory part of this essay however, 

 it has been demonstrated to be contrary to all analogy, that 



