new Species of Crinoids. 1(33 



height of the calyx, measuring to the distal margin of the 

 interbrachial plates, varies from 18 to 23 millim. in different 

 specimens, and is slightly less than their width, which varies 

 between 20 and 25 millim. 



Basals. — The base of the calyx has the form of an open 

 shallow cup, the margin of which is hexagonal in figure, with 

 indistinct angles. The lower exterior portion where it connects 

 with the stem is circular, about 5 millim. in diameter, with a 

 slightly projecting collar, the edges of which are finely 

 grooved (PI. VI. fig-. 2). Within this is a slight depression 

 and at the bottom of it a small circular aperture communi- 

 cating with the interior of the calyx. The base is formed 

 by three equal plates of a pentagonal form. The basal plates 



16--' 



2'b.A 



Diagram of Hystricrinus Carpenleri, natural size. 



A, anal plate ; ar, arms ; B, basals ; lb, interbrachial plates ; lb. A, inter- 

 brachial anal plates ; hit, interaxillary plate ; pi, pinnules ; R, first 

 radial ; i2 2 , second radial ; R, third or axillary radial. 



vary from "3 to '6 millim. in thickness near their upper mar- 

 gins, whilst near their bases they are from 1 to 2 millim. in 

 thickness. The base itself varies from 5 to 7*5 millim. in 

 height, and is thus about one third the entire height of the 

 calyx 5 it is from 14 to 21 millim. in width. The upper 

 margins connecting the basals with the radials are not exactly 

 straight, but rudely crenulate, the edges slightly overlapping 

 the radial margins. 



