PLATE XVII. 



1. Joints of the stem of specimen (Xo. 8) adjoining the calyx, with alternating ribbed and flat joints. 



and serrated sutures (*). 



2. Curved part of the stem of specimen (Xo. 8) immediately below the joints shown in Fig. 1 (eight 



rings, more or less crushed, to be intercalated between Figs. 1 and 2). 



3. Part of one of the crushed rings showing edge of rib of one joint, a flat joint with the wedges of a 



new joint both above and below it (\). 

 4 The joints of the upper part of Fig. 2. at point marked a (*). 



5. The joints of the same stem at point marked 6. 



6. The joints of the same stem at point marked c. 



7. The joints of the same stem at point marked </. 



8. The curved upper portion of the stem of specimen X*o. 1, showing the passage of the smooth rings 



into ribbed and flat joints, more and more serrated in proportion to their distance from the 

 calyx (f). 



9. Joints of the stem of specimen No. 1 adjoining the calyx, with smooth or slightly serrated sutures 



and isolated granules gradually passing into coarse tubercles connected by horizontal ridges (*). 



10. The opposite side of the stem of Fig. 9. 



11. A few rings of the middle part of the stem of Fig. 8 at a, to show the prominent transverse ridges 



and the flat rings, both with finely serrated sutures (|). 



12. 13. Parts of astern (of another specimen?) slightly curved, in which the ribs have passed into 



a mere angular outline of the joint (f). Figs. 12 and 13 are contiguous parts of the same stem. 

 11 Magnified joints of stem of Fig. 12 at point marked a (*). 



