360 THE VOYAGE OF H.M.S. CHALLENGER. 



Tlie Cortical Shell is commonh' simple (PI. 39, figs. 12, 18), sometimes composed 

 of two concentric shells (PI. 39, fig. 13), rarely of three. As in the Artiscida, also in 

 the Cyphinida, from both poles of the main axis solid spines or hollow fenestrated tubes 

 are often developed (PL 39, figs. 14, 16-18). 



The Central Capsule of the C}^hinida (PL 39, fig. 13) is of the same form as in 

 the Artiscida, generally ellipsoidal, but -odth an equatorial ring-like stricture, which 

 divides it into two equal halves. It encloses the simple or double medullary shell, and is 

 perforated by the radial beams starting from this. From the inner surface of the 

 surrounding cortical shell it is separated by a thicker or thinner jelly-layer, the calymma. 

 (Compare also Taf. xsii. fig. 14 of mj^ Monograph, 1862.) 



Syiiojisis of the Genera of Cyphinida. 



( Medullary shell simple, . 155. Cyphaidu. 

 Cortical twin-slieU simple. • 



( Medullary shell double, . 156. Cyplionium. 



Cortical twin-shell double i Cortical shell double, . 157. Cypaasis. 



or triple; medullar}' shell 

 double. ( Cortical shell triple, . .158. CyplwcoJiins. 



„ ■. 1 ■ { Medullary shell simple, . 159. Ctiphiaus. 



Ivvo opposite polar spines J "' '^ •^'- 



\ V ^' )■ y Medullary shell double, . 160. Cyphinidium. 



,„ -1 I 11 j> ( Medullary shell simple, . 161. Cannartiifcus. 



Iwo opposite hollow lenes- ) ■' ^ 



" ■ ( Medullary shell double, . 162. Cannnrtldium. 



Cortical shell without 

 peculiar spines or hoUow 

 fenestrated tubes on both 

 poles of the main axis. 



Cortical shell simple, with 

 peculiar spines or hoUow 

 fenestrated tubes on both 

 poles of the main axis. 



\ 



Genus 155. Cyphanta,^ n. gen. 



Definition. — Cyphinida with simple cortical shell and simple medullary .shell, 

 without polar spines or tubes. 



The genus Cyphanta is the most simple of all Cyphinida, and can be regarded as 

 the common ancestral form of this family. It may be derived phylogenetically from 

 Druppula by a ring-like constriction in the equatorial plane of the ellipsoidal corticnl 

 shell, or from Artiscus by secondary formation of a central (spherical or ellipsoidal) 

 meduUary shell. 



Subgenus 1. Cyphantella, Haeckel. 

 Definition. — Surface of the cortical shell smooth, without spines or thorns. 



' Cyplm,nta=Ki'0ccuTiic, Mediterranean port in Laconia. 



