EXPLANATION OF PLATE IIL 



PHOTOGRAPHED FROM THE MEMOIRS, GEOL. SUR., UNITED KINGDOM. 

 DECADE VII, PLATE IV. 



Fig- 1. Cryptonymus sexcostatus, a coiled specimen ; from 

 Khiwlas --page 25. 



Eig. 2. Ditto, back view, to .show the 11 thorax segments. 



Fig., 3. Ditto, showing the raised fascia a. 



Fig. 4. Ditto, side view. 



Fig. 5. Imperfect cephalic shield ; the dotted lines are added from 

 other sjaecimens ; the cheeks show the jjitted surface. 



Fig. 6. Magnified portion of cephalic shield. 



Fig. 7. A thorax segment enlarged ; at a, the fulcrum point ; b, 

 the facetted surface, n,ud e, the blunt indented tip, as usual in 

 the genus ; they are represented by dotted lines. 



Fig. 8. Side view of the pleurse in a coiled state ; at a, one of the 

 facetted surfaces is seen by the breaking away of the other 

 segments. 



Fig. 9. Pygidium of a Rhiwlas specimen. 



Fig. 10. Pai't of the saiae, magnified, to show the scabrous surface. 



Fig. 11. Variety of the pygidium with 7 pleuras. Rhiwlas. 



Fig. 12. Internal cast of variety with the central part of the axis 

 more free from ribs. Sholes Hook. 



Fig. 13. Front view of the cephalic shield, slightly enlarged, of 

 Cryptonymus variolaris, to show the course of the facial suture 

 in front of the head, and the vertical suture b, which divides 

 the cheeks, filled at its lower end by a narrow triangular ros- 

 tral shield. Wenlock limestone of Dormington, Woolhope. 



Fig. 14. The same, a side view ; a a, facial suture. 



Fig. 15. Under view, somewhat enlarged, of the pygidium of 

 CryplonyviusiJundatuH, to show the incurved scabrous margin 

 which unites the lateral ribs of the pygidium ; their free points 

 are seen projecting beyond it. Walsall, near Dudley. 



Fig. 16. Hypostoma of the same enlarged; a, sinuated margin; 

 b, cncuUate base ; c, the points of the extended base of attach- 

 ment. Walsall. 



Fig. Cryptonymus Nereus. Hall. From the 20th Regents' 

 Report, N. Y. State Cabinet, page. 24. 



