Report of U. S. National Museum 1901. 



Plate 63. 



THE DORSAL CUP. 



The Dorsal Cup in its s.mplest form is composed of 2 or 3 circlets of s plates, those in 

 one circlet alternating with the 5 in the adjacent circlet. Of these the most important 

 are those that support the brachia and to them the term raMak is restricted .colored bluel 



colored red', so called because in many 

 on the stem. Such crinoids are called 

 occurs beneath the basals (colored yel- 



The interradial plates below these are the 

 crinoids they form the base of the cup an 

 ■' "■•• In other crinoids a circlet of mr 

 low , and these, therefore, are known is 



Primarily there are 5 plates m each circlet, but owing to the fusion of two or more 

 o. the proximal plates the number of basals in monocyclic forms may be reduced to 4 3 

 or even 2, and the infrabasals in dicychc crinoids to three. 



The cup often has, in addition to the plates above ' described, supplementary plates 

 known as anals and tut „■../., which assist in enlarging the cup. 



776. Batocrmus longiio 

 7.519- Platycrinus planu: 

 24,191. Cyathocrinus mull 



r Carbo 



The cup pla 



the intrrbracki 



Crinoid Series— the Dorsal Cup. 



