Plate III. 

 Pourtalesia Jeffreys! Ww. Thoms. 



TliL' ;iiiil)ul:\(T:tl system coloured. 



Fig. 10. The ventral half of the skeleton, seeu from the inside. The hetfronoray marked as in tia;. 9. 



Fig. 11. The dorsal half of the skeleton, seen from the inside. 



Fig. 12. The infra-frontal recess seen from the peritoneal cavity, and from tlie left. 



Fig. 13. Longitudinal section of the hindmost part of the skeleton, the caudal prolongation, the periproct, 



and the anal membrane: atn. 

 Fig. 14. The dorsal termination of the ambulacrum V. from the inside. 



