I \l \M(M i;i\i s DIOMl D I I.; 



to have as great relationship with the more recenl Crinoids like Millericrinus 

 as with the certain palaeozoic types like Poteriocrinus. 



Meek gives in Volume 1. of the Report of the Geological Survej of Ohio, 

 Plate II. Figs. •">'. '■'< , a view of the vaull of Glyptocrinus O'Nealli, showing 

 it to consist of a large number of minute pieces, with large interradials. 



In Saccocrinus* the plates of the calyx certainly pass from the ba 

 gradually as is possible to the edge of the base of the anus, from large 

 plates to smaller ones, and still smaller ones forming the vaultj and the 

 easts figured show most distinctly the course of the subtegminal ambulacra 

 and the great development of the interradial system. 



In Glyptoci'inuSjf .Miller states that he lias most distinctly traced the con- 

 tinuation of the vault up the inner sides of the arms tor the distance of 

 an inch above the vault. The pinnules do not cover the ambulacral grooves. 

 The vault plate's become smaller as they approach the inner face of the 

 arms, and, continuing to diminish in size, form a somewhat granular con- 

 tiguous element that covers the amluilacral furrows. The anal plates are 

 large, forming an irregular pyramidal structure. 



The latest views of Wachsmuth and Springer on the nature of the vault 

 of Crinoids may be summed up from their own statements. We do not 

 materially gain in our comparisons by taking into account the manifold 

 types of structure in the calyx of palaeozoic Crinoids which culminate 

 in the subcarboniferous period; and we really need to take into service 

 only those of the principal types which have the greatest palaeontological 

 range, and help us distinctly in our understanding of the more recent 

 Crinoids. 



In the Articulata of Wachsmuth and Springer, where the vault has 

 been observed, it is found to consist of many small irregularly arranged 

 plates, is more or less flexible, the ambulacra are subtegminal, and in 

 the Ichthyocrinidae possess a small anal proboscis. 



In the Camerata the vault, on the contrary, is composed of large massive 

 plates; and in many types a regular arrangement has been traced in the 

 dome plates, which, however, it is often very difficult to trace in groups 

 in which the anal proboscis takes a great development, or where the vault 

 is composed of more numerous plates; and the relationship of this vault 



* S. A. Miller, Journ. Cincinnati Soc. of Xat. Hist., 1881, Vol. IV. Plate IV. 



t Glyptocrinus re-defined and restricted, by S. A. Miller, Journ. Cincinnati Soc. of Nat. Hist., 

 1883, Vol. VI. p. 217. Plate XI. 



