9 



specimens, that they unite with the plates of the vault. Probably 

 they do not, but as the sutures are destroyed this cannot be de- 

 termined. 



The limestone matrix covers the greater part of the vault, in 

 our best specimen, so that but little can be said of it beyond what 

 is shown by the illustratiou. It is characterized, however, by a 

 plate over each double radial series which bears a very long, strong 

 spine. The broken ends of spines belonging to other plates are 

 preserved in the matrix, but there is no evidence of a proboscis. 

 The summit of the vault is apparently below the top of the matrix 

 shown in the illustration, and not as high as the top of the spines 

 over the radial series. 



There have been described, heietofore, only two species bear- 

 ing twenty arms — D. lamellosus and D. iroosii—&nd this species 

 is so far removed from them that comparison is unnecessary. 



Found in the Hamilton Group, at Charleston, Indiana, and now 

 in the collection of Wm. F. E. Gurley. 



DOLATOCBINUS LACUS, Lyou. 



Plate I, Fig. a, side rietc: Fig. 7, basal riew. 



Lyon described the body as "subglobose, truncated below, col- 

 umnar pit broad and deep; summit somewhat conical, prolonged 

 by a proboscis: column round, columnar perforation rather large 

 and pentalobate." He said; "The body is adorned by a most 

 beautiful network of raised triangular figures; the points of the 

 principal triangular figures rise from, and terminate at the center 

 of the first interradial pieces; a subordinate set of figures terminate 

 at the center of all the pieces below the arms. In some spec- 

 imens the lines are continuous, in others, interrupted. The sum- 

 mit pieces are sometimes adorned by a single prominent granule; 

 in other specimens, many of the pieces are ornamented by a num- 

 ber of granules, arranged in lines across some of the pieces in 

 nearly parallel rows, or in a circular band around a more promi- 

 nent central one." 



Our specimens agree with the above description and in compar- 

 ison with other species we would note the high calyx, with a slight 

 constriction below the arm bases, the flattened or truncated base, 

 and pentagonal, funnel shaped, columnar pit, bounded externally 

 —2 G. 



