EEVISIOX OF PALEOZOIC STELLEROIDEA. 271 



"On the dorsal side of the body * * * there is seen a compar- 

 atively large circular area or disk, composed of an outer circle of ten 

 rather prominent pieces, united together in five pairs by close-fitting 

 sutures, each piece being pierced by a round ovarian ? pore. Imme- 

 diately within tliis circle there is, apparently, another circle of ten 

 smaller pieces, also united in five pairs, but without pores; and within 

 this latter circle there is a third range of five still smaller, nonporif- 

 erous pieces, surrounding a central anal? opening; the whole re- 

 minding one of the apical disk of an Echinoid, though dift'ering in 

 structure from this part of the Imown types of that group. It is 

 also worthy of note that there is some analogy between this disk and 

 the body of a crinoid, excepting that there is a central opening, and 

 that the first division of the radial series takes place immediately on 

 the inner range of pieces corresponding to the basal pieces of a crinoid, 

 while all of the third range of pieces are pierced by pores. * * * 



''Immediately outside of the circle of ten pore pieces, mentioned 

 above, each pair of these pieces is succeeded by two or three pairs of 

 difl'erently formed, interlocking, transverse pieces, in direct range, con- 

 necting them mth the dorsal side of each of the five rays. A little far- 

 ther out the dorsal side of the rays, these transverse pieces are seen 

 to become disconnected by more or less wide spaces, and gradually 

 pass into pairs of lanceolate pieces, deeply furrowed longitudinally, 

 while between the inner ends of the two pieces of each pair there 

 appears to be a porelike opening. These latter disconnected pieces 

 continue all the way out to the extremities of the rays, and, with 

 numerous smaller intervening ossicles, form together, as it were, the 

 skeleton or framework of the long flexible rays. It is only, however, 

 when an outer granular integument has been removed that this 

 skeleton structure can be seen. In some parts of some of our specimens 

 this outer granular covering remains, and is seen to be composed of 

 numerous small, rounded, rather prominent ossicles, regularly 

 arranged in qui[n]cunx, so as to give the surface a chagreenUke rough- 

 ness. These ossicles were doubtless attached to, and secreted by, a 

 soft dermal envelope, covering the whole surface, while the larger 

 pieces within formed the frame, as it were, of the whole structure, 

 and probably furnished points of attachment for the muscles that 

 moved the rays. 



"None of our specimens show clearly the inner side or ambulacral 

 furrows of the rays, nor the under side of the body — consequently 

 we know nothing of the nature or position of the mouth or of the 

 ambulacra. In several instances, however, we have seen the remains 

 of one or more rows of small, short, longitudinally striated spines 

 along the inner side of the arms. 



50601°— Bull. 88—15 18 



