REPORT ON THE RADIOLARIA. 



307 



of a double medullary shell (PL 39, fig. 4). From these two genera all other forms 

 of the subfamily may be derived. 



The Central Capsule of the Druppulida is constantly ellipsoidal, larger than the 

 concentric enclosed medullary shells, smaller than the surrounding cortical shell ; it is 

 separated from the inner surface of the latter by a thinner or thicker jelly-mantle. 



Synopsis of the Genera of the Druppulida. 



Cortical shell without 

 polar appendages 



(neither solid spines 

 nor hollow tubes at 

 the poles of the main 

 axis). 



Cortical shell simple, ellip- 

 soidal. 



Cortical shell composed of 

 two or more concentric 

 shells. 



Surface 

 smooth, . 



double. 



spiny, 



Two opposite solidspines, 

 arising from the poles - 

 of the main axis. 



Two opposite hollow "1 

 fenestrated tubes, aris- I 

 ing from the poles of [ 

 the main axis. J 



Cortical 

 shell simple, - 

 ellipsoidal. 



Medullary f Both P olar s P ines e 1 lla1 ' 



shell simple. ) ,, ,, , 



( Both polar spines unequal, . 



Medullary j Both P olar s P ines e 1 ual > 



shell double. 



Both polar spines unequal, . 



Corfical shell composed of two or more concentric shells; 

 medullary shell double; both polar spines equal, 



Cortical shell simple, ellip- j Medull "y shell simple, 



soidal. ) .... , 



( Medullary shell double, 



131. Druppula. 



132. Driqrpocarpm. 



133. Prunulum. 



134. Prunocarpus. 



1 35. Cromyodruppu. 



136. Cromyocarpus. 



137. Lithatractus. 



1 38. Druppairachis. 



139. Stylatractus. 



140. Xipliatractus. 



141. Cmmi/ofractus. 



142. Pipetta. 



143. Pipettaria. 



Genus 131. Druppula, 1 n. gen. 



Definition. Druppulida with simple ellipsoidal, cortical shell, and simple 

 medullary shell, without spines or polar tubes. 



The genus Druppula, as the simplest form of the Druppulida, may be regarded as the 

 common ancestral form of this subfamily. It may be derived phylogenetically either 



1 Druppula- Small drupe or SJMTTT*, ripe Olive. 



