PLATE XVI. 



Var., with two plaits on mesial fold, Ter. bidens 



of Phillips, nat. size. 

 A young shell, with two plaits. 

 A var., with three plaits on mesial fold, Ter. 



triplicata of Phillips, nat. size. 

 A variety with three plaits from another locality. 

 A young shell, with three plaits. 

 A variety, with four plaits. 

 The type form of the species. 

 A less aged and more elongated specimen. 

 . Four varieties, nat. size, showing a difference 

 in the number of the plaits ; fig. 9 is the 

 largest example I have seen. 

 13, 14. ,, lacunosa. I am not quite certain as to this determination; 



the specimens much resemble some German 

 types of R. lacunosa. 

 15. „ ? This shell is from the Lias of Sky, and my only 



inducement to figure it here is on account of 

 the variety of Liasic species of Brachiopoda 

 in Scotland. It has much the appearance 

 of some young specimens of T. quadriplicata 

 of Zieten. 



Fig. 













1. 







Rhynchonella 



variabilis. 



2. 







11 





>> 



3. 

 4. 







11 



11 





n 

 11 



5. 







11 





>> 



6. 







n 





■>■> 



7. 







n 





plicatella. 



8. 







11 





3) 



9, 10, 



11, 



12. 



11 



sub-tetrahedra, 



