PLATE XXV. 



1. Two rings of a part of the stem corresponding to that of Fig. 5'^, Plate XVIII. 



2. Transverse view of two rings from the same part of the stem. 



3. Proximal face of segment of one of the above rings. 



4. Distal face of a ring on a part of the stem a few rings above. 



5. Sutures of a part of a ring in which the serrations are coarser than in Fig. 1. 



6. Portion of face of same ring, in which the radiating ridges are quite numerous. 



7. Transverse section of same ring, showing the thickening of the outer edge, with a comparatively 



large axial canal. 



8. Axial fibrillte and facial muscular ligament connecting faces of adjoining rings. 



9. Ring from a part of the stem corresponding to that of Fig. 7, Plate XVI II. ; the outer serrations 



have nearly disappeared. 

 10. Irregular serrated plates forming the radiating ridges from the middle third of the face of the 

 joint. 



