CRINOIDS AND BLASTOIDS. 205 



of hydrospires, eight to each group. The spiracles are reduced 

 to an elongate slit-like opening, wider above than below, not 

 visible when the pinnules are in situ, but quite conspicuous when 

 these are wanting, large enough that we could observe at the 

 bottom of two of them the clefts of four and six hydrospires 

 respectively. Anal opening very narrow, decidedly slit-shaped, 

 and strictly lateral. 



Geological position, etc. : The same as the last. 



The figured specimen is in our own collection : the description 

 of the ambulacra and hydrospires was made from a beautiful 

 specimen kindly presented to us by Prof. W. H. Harris, which 

 we received too late for illustration. 



March. 1887. 



P. S. This paper was placed in the hands of Prof. Worthen 

 early in the spring of 1887, before we had made the discovery 

 that the so called "central plate" and the four "proximals" at 

 the summit of Blastoids and Crinoids represent the orals, and 

 this accounts for the fact that the old terms are used in the 

 descriptions. 



