2 



Page 

 Fig. 13. Cross section of the same at its upper end, showing the ambulacrum in the narrow 



sinus, and the hydrospircs buried in the substance of the plate. Natural size. 95 

 Fig. 14. Cross section of a radial plate with the hydrospires imbedded in its substance. 



Probably of a different species. Subcarboniferous, Indiana. Coll. Wachsmuth. 



x3 95 



Metablastus Wachsmuthi, Gurley, sp. 

 Fig. 15. Summit view of a much decorticated example, showing the positions of the anus 

 and of the double spiracles, &c. Subcarboniferous, Indiana. Coll. Wachsmuth. 

 x3 110 



El^acrinus Verneuili, Troost, sp., p. 216. 



Fig. 16. Summit view, showing the position of the anus, the double spiracles, and the 

 central vault-plates covering the peristome. Corniferous Limestone, Kentucky. 

 x4 74 



Fig. 17. Portion of an ambulacrum, showing the side plates meeting in the middle line, tear- 

 shaped outer side plates (on the right side only), large pores, and the transverse 

 grooves on the deltoid plates corresponding to them. x 12 36 



Fig. 18. Portion of another ambulacrum, with outer side plates on both sides. x 12. . 56 



El^acrinus lucina, Hall, var. Canadensis, Montgomery, var. 

 Fig. 19. Anal interradius, showing the position of the anus, and the posterior deltoid divided 



by the anal plate. Upper Devonian, Ontario. Coll. J. G. Hinde. x 3. . . 36 



