CLEIOCRINUS. 107 



walls, are characters common to both. Of course the fixation of pinnules is 

 accomplished in different ways, being in Reteocrinus by means of supplement- 

 ary plates, while in Cleiocrinus it is simply by lateral union of brachials and 

 pinnules. Aside from the great strengthening of the radial and anal series. 

 the calyx of Reteocrinus is not so very much unlike that of Cleiocrinus. It is 

 built up of a large number of thin plates, evidently forming a pliant wall be- 

 tween the rays. Its calyx was clearly pliant, and the disk conspicuously so. 

 I have more than a hundred specimens of R. onealli which were preserved 

 in a very fine, soft, calcareous mud, and in almost every case the calyx is 

 flattened, and the disk more or less bulging in a variety of shapes, as if it 

 were extremely flexible. It is really a thin integument of very small plates, 

 without definite arrangement. I am unable, however, after close examina- 

 tion of a large series of well preserved disks, to find any trace of ambulacral 

 furrows upon the surface, nor of any opening for the mouth. The anal open- 

 ing is clearly indicated in some cases ; it is not conspicuous, and evidently 

 was often entirely closed, or concealed by the contraction or folding of the 

 in tegument. 



I have figured a number of excellent specimens of this species, for com- 

 parison on these several points (PI. I., Figs. 14 to 21). A careful study of a 

 large number of these specimens, in unusually good preservation, leaves no 

 reason to doubt the correctness of the assignment of the group to which they 

 belong to the Camerata. The mouth and ambulacra are undoubtedly sub- 

 tegminal. But it seems to me that they, with the addition now of Cleiocri- 

 nus, lie in the borderland closely approximating the Flexibilia, and should be 

 considered as intermediate forms. This would accord with the opinion fre- 

 quently expressed in private correspondence by P. II. Carpenter, who was 

 much impressed by the strong resemblance of the Reteocrinida? to the 

 Ichthyocrinidaj. 



