^6 PROCEEDINGS OF THE ACADEMY OF [1887. 



Shumarcl's figure. At a hasty glance there seem to be six pieces, a 

 central one surrounded by five others ; but when examined under a 

 strong magnifier there appear two pieces in the center, and six sur- 

 rounding them. From this one spiracle, the arrangement of the 

 supposed plates in all the other openings was probably inferred, and 

 the figure made accordingly; for the arrangement of the so- 

 called plates at the- four other openings is altogether different, and 

 very irregular. So we find at the anal opening a good sized Gaster- 

 opod beside other pieces. 



The central opening is covered by a single, comparatively large, 

 elongate body, ovoid in form, which does not actually close the open- 

 ing, but rests inside of it, beneath the level of the deltoids, slightly 

 touching them. Its position is such that if it represented the sum- 

 mit structure, the food grooves could not have entered the peristome 

 This is also one of those foreign bodies to which we alluded, but its 

 surface is too much worn to say much about it. 



Etheridge and Carpenter ^ express some doubt of the correctness 

 of Shumard's description as to the plates covering the spiracles, 

 although they take Hambach to task (pp. 68, 164) for disputing 

 the same description as to the covering of the central opening. 

 They allude, however, to White's discovery of a plated integument 

 over the anal opening in Orophocrinus stelliformis, which we are 

 able to confirm. This covering we have found well preserved, not 

 only in 0. stelliformis, but also in two new species which we de- 

 scribed for Vol. VIII. of the Illinois Report now in prepara- 

 tion. In all cases where we found this structure intact, it lies below 

 the level of the deltoid through which the aperture penetrates, and 

 is composed of a large number of small, irregular pieces without any 

 visible opening. 



We do not mean to say that the peristome and spiracles were not 

 covered by plates in P. conoideus, but we do assert that there was 

 no such covering as figured by Shumard. Even in the shape of the 

 spiracles his figure is totally erroneous. He represents them as very 

 regularly pentangular, so as to receive the five supposed plates neatly 

 filling the angles, and as surrounding a central one, one of their sides 

 facing the central opening instead of an angle. The fact is, however, 

 the spiracles are not pentangular but quadrangular, somewhat un- 

 equally diamond-shaped with sides slightly curving, the outer angle 

 obtuse, conforming to, and in fact formed by, the slope of the side 



^ Catalogue of the Blastoidea, p. 69 



