46 



This is till' first species of Dohilocrinus that lias i)Pen dc 

 scribed having thirteen arm openings to the vault and henct> 

 the arm foi-mula 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 (leo. K. Greene, in 

 the Hamilton (Iroup, near Charlestown, Indiana, and now in 

 tlie collection of Wrn. P. E. Gurley. 



noi.ATOCRiNus cism.A. n. sp. 



I'hile III, Fig. 7, Ixisnl riew; Fiij. 8, siinniiil vieir; Fig. 9, side 



vieir. 



Species medium size and handsomely sculptured. Calyx sul)- 

 hemispherical, slightly constricted below the arms and broadly 

 truncated at the ba.se. 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 cin(iue 

 foil canal. 



Basal \)lates form a pentagon one fourtli 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 i-ay on the right of the azy- 

 gous ai'ca and in the left lateral ray, support on each uji]>er 

 slo])ing side a single .'secondary radial, which is axillary and 

 liears njioi: each ujtper side two tertiary radials, vi-hich gives 

 to each of tiiese lays four arms. In the ray on the left of the 

 azygous area and iu llic one on the right Inteiai side the thii-d 

 priuuiry I'adiais support on om^ ujiper sloping side thi"ee sec- 

 ondary radials, and on the other a single siH'ondary radial that 

 is a.xillary and bears upon each upper side two tertiary radials, 

 whicli gives to each of the.se rays three arms. Lt is the jirox 

 imal lay 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 



