CRINOIDEA. 



125 



is a series of plates which are termed "basal" from their 

 position, and which constitute the " pelvis " of Miller. The 

 "basals" may be five, four, or sometimes three in number, 

 and they form the lowest portion of the cup. In some cases 

 the "basals" are succeeded by a second row or cycle of plates, 

 which should properly be regarded, with Professor Beyrich, as 

 a second series of basals, but which are sometimes regarded 

 as something special, and are termed the "parabasals" or 

 " sub-radials." The basals (fig. 79, b) are succeeded by a 



Fig. 79. Diagram to show the structure of the calyx in the fossil Crinoids ; b Basals; 

 r Radials; i Inter-radials ; a Anal plates. Calyx of Forbesiocrinus. (After Pictet.) 



series of two or three rows of plates, which are directly super- 

 imposed upon one another, and which form the foundations of 

 the arms (r, r). These are termed the "radials" (the " cos- 

 tas " of Miller), and are termed " primary," " secondary," and 

 " tertiary," according to their distance from the basals. The 

 last radial plates, or those furthest from the column (some- 

 times called the " axillary radials "), give origin to the arms. 

 The radial plates are arranged in a series of vertical columns, 

 which extend from the summit of the basals to the bases of 

 the arms. Between the different columns of radial plates, 

 however, are intercalated certain other smaller plates, which 







