26o CALIFORNIA ACADEMY OF SCIENCES. [Proc. 3D Ser. 



EXPLANATION OF PLATE VL 

 Pontoscolex corethrurus (Fr. Muller), mexicanus, subsp. nov. 



Fig. 17. Longitudinal section of the body-wall in somite IV, showing the 

 arrangement of the muscular layers. 



Fig. 18. Cross-section of part of the body-wall in somite IV. Zeiss D., Oc. 

 4. The letters indicate the same as in fig. 17. 



Fig. 19. Cross-section of the body-wall in one of the clitellar somites, show- 

 ing tubercula pubertatis. 



Fig. 20. A highly magnified part of the tubercula pubertatis, Zeiss ^^, Oc. 2. 



Fig. 21. Part of the body-wall from the caudal zone, showing the various 

 epidermal cells. 



Fig. 22. An isolated vibratory sense-cell. 



Fig. 23. Cross-section of the worm, one of the somites containing calciferous 

 diverticles. 



