﻿PLATE XVIII. 



Fin. 

 1,2, '2, a. 7Vu/o}//a ////jl/osr/. Sow. Varicfy with ])roiniiieiit nodose co.st;p aiul wide 



aiite-cariiial spaee. Portland Oolite, Tisbiiry. Also 

 Plate XXI, fig. 1. (Page 84.) 



3. ,, Damoniaiia, De Lor. Variety with few large nodes upon the 



costae ; see also Plate XXI, figs. 2, 3, 4, 5. 

 Portland Limestone, Portland. (Page 88.) 



4. „ /jibbona. Variety witli the costae small, partially plain or sub- 



tuberculated ; see also Plate XIX, fig. 2. Portland 

 Oolite, Tisbury. (Page 84.) 



5. 6. „ (jibhosa. The typical form, longitndinal sulcations strongly 



defined. Portland Oolite, Tisbury. (Page 84.) 



