46 



This is the first species of Dolatocrinus that has been de- 

 scribed having thirteen arm openings to the vault and hence 

 the arm formula alone will distinguish it from all other 



species. 



The specific name is in honor of the late Sydney S. Lyon, 

 who established the genus. Found by Geo. K. Greene, in 

 the Hamilton Group, near Gharlestown, Indiana, and now in 

 the collection of Wm. F. E. Gurley. 



DOLATOCRINUS CISTULA, XL. Sp. 



Plate Ifl, Fig. 7, basal view; Fig. 8, summit viciv; Fig. 9, side 



view. 



Species medium size and handsomely sculptured. Calyx sub 

 hemispherical, slightly constricted below the arms and broadly 

 truncated at the base. Radial ridges rather large and bearing 

 sharp, elongated nodes. Surface of all the plates bear more 

 or less elongated nodes, and there are a few radiating lines on 

 the first interradials. Column round and having a large cinque 

 foil canal. 



Basal plates form a pentagon one fourth wider than the 

 diameter of the column, having an hemispherical depression 

 or cavity for the insertion of the end of the column. First 

 primary radials wider than long, and subequal in size. Second 

 primary radials large, quadrangular and nearly as long as 

 wide. Third primary radials rather larger than the second, 

 pentagonal, axillary, and, in the ray on the right of the azy- 

 gous area and in the left lateral ray, support on each upper 

 sloping side a single secondary radial, which is axillary and 

 bears upon each upper side two tertiary radials, which gives 

 to each of these rays four arms. In the ray on the left of the 

 azygous area and in the one on the right lateral side the third 

 primary radials support on one upper sloping side three sec- 

 ondary radials, and on the other a single secondary radial that 

 is axillary and bears upon each upper side two tertiary radials, 

 which gives to each of these rays three arms. It is the prox- 

 imal ray adjoining the azygous area that bears the tertiary 

 radials. In the ray opposite the azygous area the third primary 

 radial "supports upon each upper sloping side three secondary 



