58 



This species bears more resemblance to Dola'ocrinus bellulus 

 than to any other, but is readily distinguished by having only 

 sixtoen inst3ad of sevent3en arms, and by having no 

 ovarian openings. There is also some difference in the con- 

 vexity and structure of the vault and in the surface ornamenta- 

 tion. 



Pound in the Hamilton Group, near Charlestown, Indiana, and 

 now in the collection of Mr. J. F. Hammell, of Madison, Indiana. 



DOLATOCRINUS SACCULUS, n. Sp. 



Plate III, Fig. 11, basal view; Fig. 12, side view. 



Species medium or below medium size. Calyx subhemi- 

 spherical, broadly truncated at the base and subcylindrical 

 above. Radial ridges consisting of small, rounded elevations, 

 which are interrupted by central nodes on the plates. Surface 

 ornamented with radiating ridges from the central part of the 

 plates that do not unite with the radial ridges or coalesce 

 with the central nodes. The radiating ridges are toward the 

 margin of the plates, and the second interradials have no cen- 

 tral nodes. Column round, medium size, and having a large 

 cinque foil canal. 



Basal plates hidden by the column and a rounded flanging 

 rim that surrounds it, on the basals and at the commencement 

 of the first primary radials. First primary radials a little 

 wider than long, and subequal in size. Second primal y radials 

 rather less than twice as wide as long, quadrangular, sides 

 nearly parallel. Third primary radials very little larger than 

 the second, from one-half wider to twice as wide as long, pen- 

 tagonal, axillary, and bear upon each superior sloping side a 

 single secondary radial. The secondary radials bear upon each 

 superior sloping side a single tertiary radial, which gives to 

 this species twenty ambulacral openings to the vault. 



The first interradials are rather large and have nine sides. 

 There is only a single plate in the second range and it ex- 

 tends to the top of the calyx and connects with the plates of 

 vault. The azygous area is not materially different from the 

 other areas. 



The vault is moderately convex and bears rather sharp radial 

 ridges. The sutures cannot be distinguished in our specimen. 

 There are twenty ovarian apertures, one on each side of each 



