Plate IV. 



Pourtalesia Jeffreysi Wyv. Thoms. 



Pig. 15. The sub-labial region, from the outside, showing the arabulacrals 1 1 and Vi, \1 a 1 and b 1, 



IV a 1 and bl, the four spherids, p. 40, and the four pedicellar peripodia. 

 Pig. 16. The same from the insida, showing the part bent in into tlie infra-fronfal recess, the niinute iabrum, 



5, and the four pedicels. 

 Fig. 17. Part of the same, placed so as to show the internal trabecules. 

 Fig. 18. The infra-frontal recess, p. 7, 28, scen from the peritoneal cavity, and from behind, sliowing the 



peristome with the buccal membrane and a part of the oesophagus, the neural collar (and vessel) 



and the raain trunks proceeding from it. 

 Fig. 19. The same, from the left side. 



Fig. 20. The buccal membrane, with the oesophageal opening, p. 29. 

 Fig. 21. The top of a sub-labial pedicel. 

 Pig. 22. The same, in a state of contraction. 

 Pig. 23. One of the sexual tubes. 

 Pig. 24. A part of the palate of the infra-frontal recess, showing its crowded tubercles and a niinute pore. 



