49 



Tills species is most nearly related to DAalocrinus charles- 

 ioiciiensis, with which it agrees in having fifteen arms. But 

 the arms are not distributed in the same way. In this species 

 the four-armed ruy is opjjosite the azygous area, in that species 

 a three-armed ray is ()pi)osite the azygous area and the four- 

 armed ray is lateral. In this species the secondary series and 

 single arm adjoins the azygous area on each side, in that 

 species the secondary series and single arm adjoins the azygous 

 area upon one side and the tertiary radials and double arm 

 on the other. These structui-al differences must separate the 

 species, though the vaults are also quite different in form and 

 ilo not agree in the number of the plates, and the surface 

 mark'ings are not the same. 



Pound by Creo. K. Greene, in tlie Hamilton Group, near 

 Charlestown, Indiana, and now in the collection of Wm. P. E. 

 ( ini-ley. . 



DOL.\TOCiiiNrs APLATUS, Miller and Gurley. 



[Dolafocri7ms aplatus, Miller and Gurley, Bull. No, 8 111. St. 

 Mus. Nat. Hist., ji. 4s.] 



PUilr :>. Fill. 7.7, hdsul i-iein: Fiij. 14, snmmil view; Fig. 15, 



side riew. 



We have illustrated another specimen belonging to this 

 species for the pui-pose of .showing the plates of the vault 

 which are well preserved and the sutures distinct. There are 

 slight differences in the surface ornamentation in the different 

 specimens, but the structural parts of four specimens which 

 we have now before us are the same. All of them are in the 

 colled ion of Wm. P. E. Gurley. 



nOI.ATOClUNUS ASPRATII.IS, U. Sp 



Phde .'J. Fi(j. l(i, Iinsdl view; Fit/. 17, snmmil view; Fig. 18 azyg- 

 ous side view 



Species rather below medium size. Calyx pentagonal from 

 ba.se to arms, somewhat bowl-shaped, broadly truncated, most 

 e.xpanded in the middle, and constricted below the arms. Colum 

 nar cavity pentagonal and deep. Ridial ridges angular with 

 long central nodes. Plates jiyramidal and radiately sculptured 



