ECHINODERMATA—CYSTOIDEA. 



467 



four plates ; the second, third and fourth each of five plates ; 

 the twentieth plate is very small and situated on top of the fourth 

 cycle or between it and the third cycle. Anal area consisting of a 

 pyramid of six pieces surrounded by a complete circle of many 

 small pieces. Pectinated rhombs three, one basal and two upper. 

 Ambulacra four, undivided, and usually not longer than one half 

 the length of the calyx. Anal area small, placed between the 

 second and third cycles of plates. Column tapering, composed of 

 an upper portion of about 15 plates and a thick distal portion 

 composed of many anchylosed plates coated on the outside by a 

 nodose calcareous layer. Siluric and Devonic. 



16. L. gebhardi Conrad. (Fig. 1775.) Devonic. 



Column composed of two distinct parts. Surface of calyx plates 

 granular. (Type of genus.) 



Coeymans of New York and Maryland? 



X. J^KELOCYSTis Schuchcrt. 



Calyx pear-shaped or globular, composed of 19 plates arranged 

 in circular series. First or basal series consisting of four plates. 



Fig. 1776. Jcekelocystis hartleyi^ the holotype, and enlargement of two plates, showing 

 discrete, pectinirhombs (X 8), and of the oral end, X 8- (After Schuchert.) 



the second of five plates, the third of four, the fourth of five; 

 upon the last row is situated the nineteenth plate. Anal area 

 protruding, consisting of a pyramid of six pieces. Pectinate 

 rhombs three, one basal and two upper. Ambulacra four, rarely 



