Plate IV. 



Pourtalesia JefFreysi Wyv. Thoms. 



Fig. 15. The sub-labial region, from the outside, showing tlie ambulacrals I / and V /, II a I and li /, 



IV al and b 1, the four spherids, p. 40, and the four pedicellar peripodia. 

 Fig. 16. The same from the inside, showing the part bent in into the infra-frontal recess, the minute lal)ruin, 



5, and the four pedicels. 

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

 Fig. 18. The infra-frontal recess, p. 7, 28, seen from the peritoneal cavity, and from liehind, showing the 



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



and the main 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. 

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

 Fig. 23. One of the sexual tubes. 

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



