Prof. J. Muller on the Structure of the Echinoderms, 247 



me. The triradiate 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 Echinospharites 

 aurantium, which correspond with the subjacent clefts of the 

 large plates of the calyx and their grooves. In the always 

 much worn specimen of Cryptocrinites cerasus, no indications of 

 arms have hitherto been observed. 



Forbes regards the Cystidece, like the Blastoidea, as sections 

 of the Echinoderms diiFerent from the Crinoids. The Sphceronites 

 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. Vol- 

 borth and Roemer consider the Cystidece as a group of Crinoids, 

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

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

 nites Leuchtenbergii and Protocrinites ovi/ormis the arms were 

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



The suctorial feet of the Cystideans were unquestionablyplaced, 

 as in PentacrinuSj on the ambulacral side of the arms and in the 

 calycine grooves. In the introductory part of this essay, how- 

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

 that suctorial feet should exist in any Echinoderm upon the 

 antambulacral side of the perisoma from the apical end to the 

 arms, or between the ambulacral radii. In the Cystidece, there- 

 fore, the whole calyx, with the exception of the calycine grooves, 

 is to be regarded as anambulacral. 



The genera Pentacrinus, Caryocrinus, and most Cystideans are 

 distinguished among the Crinoids by the existence of very pecu- 

 liar pores in the anambulacral plates of the calyx. Pentacrinus 

 alone has afforded the opportunity of an exact investigation of 

 these pores. I have described and figured them in the essay 

 upon Pentacrinus. 



The interambulacral (interpalmar as well as intrapalmar) caly- 

 cine pores of Pentacrinus pierce the ventral calycine plates, and 

 lead beneath the inner membrane of the calyx. They possess 

 no soft external prolongations. In contrast with the ambulacral 

 calycine pores for feet, these may be called anambulacral calycine 

 pores. Their signification is not understood, only it is certain 

 that they are not passages for feet. A comparison with the 

 respiratory pores of the Asterida suggests itself; soft tubes pro- 

 ject from these, with regard to which Ehrenberg has shown (and 

 I can confirm his statement by my own observation) that they 



