THE INDIGENOUS FAUNA. 25 



ing as it does to quite a different type from any other of the 

 Upware and Brickhill species. It is the extreme form of the 

 Idppopus group, whose nearest occurrence is at Tealby, in Lincoln- 

 shire. The plan 



Waldheimia hippopus > W. Walkeri " W. Woodwardi 



may indicate the line of evolution of this species. 



The species of the oblonga group of Terebratella fall into line 

 with perfect ease in the order indicated in the following table : 



TEREBRATELLA. GROUP A. 

 Terebratella Keeping! (Walker) 



Davidsoni (Walker) 

 oblonga (Sow.) 



1 



Meyeri (Keeping) 



,, Fittoni (Meyer). 



and moreover I find such variations amongst the allied continental 

 species that it is clear to me that with the help of a good measure 

 of specimens these also could be readily adjusted to fit into our 

 developmental series. Thus, we have in Germany, T. oblonga, 

 Puscheana and Beaumonti, and in France and Switzerland, T. 

 Meyeri [1] and semistriata. This group of Terebratella is markedly 

 characteristic of the Lower Cretaceous rocks all over Europe. 



Of the straight hinged types of Terebratella transition forms 

 occur which bind well together the two species 

 T. Menardi 



T. trifida, 



but we have at Upware and Brickhill no traces of any passage of 

 the two types oblonga and Menardi into one another. 



After having thus studied our materials with respect to their 

 interrelationships, it becomes a matter of special interest to inquire 

 into the general results and their meanings, and the interpretation 

 of those points of difficulty where our chains were weakest. 



