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



Fig. 4. Eularged end view of test, showing course of lateral fasciole across the posterior 

 extremity. 



5. Interior view of abactinal surface of test ; enlarged. 



6. Interior view of actinal floor of test ; enlarged. 



7. Interior view of actinostome ; enlarged. 



8. Actinostome, seen from the actinal side ; enlarged. 



9. Large primary tubercles of abactinal surface, adjoining apical system, in odd 

 anterior ambulacrum. 



8 (should be 10). Abactinal part of test, extending from upper part of the odd 

 anterior ambulacrum to the cluster of primary spines in the median inter- 

 ambulacral space above the anal system between it and the apical system ; 

 enlarged. 



11. Cluster of primary spines, placed above the anal system on the abactinal 

 extremity of the posterior part of the test. See fig. 3. 



11 a, h, c, d, e,f. Differently shaped primary spines. 



12. Anal system, protected by paddle-shaped primary spines round the abactinal 

 edge. 



13. Shows the outline of the anal system, with the shape of the plates covering it. 



Podocidaris prionigera, A. Ag. (figs. 14, 15), p. 59. 



14. Part of ambulacral and interambulacral regions of test, seen from the abactinal 

 side, to show the relation of the primary and secondary tubercles adjoining 

 the ambitus ; enlarged. 



15. Enlarged view of abactinal system. 



PLATE XXXV. 



Cystechinus vesica, A. Ag. (figs. 1-20), p. 150. 



Fig. 1. Seen from the abactinal pole ; natural size. 



„ 2. Same, seen in profile. 



,, 3. Same, seen from the actinal side. 



,, 4. Different specimen, showing shape assumed owing to extreme tenuity of test. 



,, 5. Interior view, seen from actinal side, to show the course of the alimentary canal. 



,, 6. Interior view of apical system and of genital organs. 



7. View of genital organs of a different individual. 



8. Actinostome, somewhat enlarged, covered with spines. 



9. Anal system, exterior view. 



