STRUCTURE OF THE OYSTIDE^. 43 



suctorial feet should exist in any Echinoderm upon the antam- 

 bulacral side of the persoma from the apical end to the arms, 

 or between the ambulacral radii. In the Cystidece therefore, 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 peculiar 

 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 (interpahnar 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 Asteridos suggests itself ; soft tubes project from these, with 

 regard to which Ehrenberg has shown (and I can confirm his 

 statement by my own observation,) that they are ceeca, which are 

 indeed connected wiih the abdominal cavity, but are perfectly closed 

 externally. 



" The calycine pores of Canjocrinus are equally without relation 

 to the arms; and thence, though differently distributed, resemble 

 the anambulacral calycine pores of Pentaainus. They occupy the 

 antambulacral part of the calyx behind the arms as far as its base. 



"Most Cystideans {Crijptocrinites cerasus excepted,) possess calycine 

 pores, which are distributed over a greater or smaller part of 

 the calyx without radiation and in a very peculiar manner. In 

 those forms with calycine grooves, as Protoainites and Sphcero?iites 

 Leuchtenbergii, these pores again appear to be anambulacral, since, 

 like the anambulacral pores of Pentacrinus, they are disposed in 

 the areas external to and between the ambulacral grooves ; here 

 however, their distribution is far wider, since they extend as far 

 as the base. 



" Two principal divisions have been made, according to the 

 distribution and combination of these pores : — 



"I. Cystideans with pore-rhombs. The pores are disposed in 

 rhomboidal figures, the one-half of which belongs to one plate, 

 the other to its contiguous neighbour. Every two pores of these 

 rhombs appear to be invariably united by canals or grooves, 



