DEVELOPMENT OF THE BRACHIOPODA 



261 



edges of the umbo, leaving an open triangular area or del- 

 thyrium in the ventral valve occupied by the pedicle. This 



108 



Cistella neapolitana Scacchi. 



FIGURE 108. Lateral view of completed cephalula stage, h, head ; d, dorsal 

 lobe of mantle; v, ventral lobe; p, pedicle. (After Shipley.) 



FIGURE 109. Dorso-ventral longitudinal section of same : showing posteri- 

 orly extended mantle lobes. A, head ; ds and vs, inner surfaces of mantle lobes 

 which are to form dorsal and ventral valves. (After Shipley.) 



FIGURE 110. Typembryo; dorsal view of larva after transformation, h, 

 head; ds, dorsal valve; hi, hinge-line of dorsal valve; p, pedicle. (After 

 Kovalevski.) 



FIGURE 111. Dorso-ventral longitudinal section based on preceding; 

 showing mantle lobes directed forward, bringing interior shell-secreting surfaces, 

 ds and vs of figure 109, on the exterior, h, head; ds, dorsal valve; hi, dorsal 

 hinge ; vs, ventral valve ; hi', ventral hinge ; p, pedicle. 



FIGURE 112. Dorsal view of early nepionic shell; showing large posterior 

 opening between valves. (After Kovalevski.) 



FIGURE 113. Profile of same, ds, dorsal valve; vs, ventral valve; p, 

 pedicle. 



condition represents the extent of the development of these 

 parts in Meristina rectirostris Hall or Gwynia capsula Jef- 



