XIV. 



SUCCESSION OF LIFE-FORMS. 



401 



AFFINITIES OF OOLITIC TEREBRATUL^E. 



grandis. 



p subundata. 

 biplicata. 



vitrea. 



carnea. 

 depressa. 



australis. 



sufflata. 

 sacculus. 



elongata. 



hastata. 



virgo. 



The 'main line' of terebratula, traced here from T. virgo in 

 the Devonian rocks, seems to experience a great gap in the upper 

 oolite group, but resumes its course in the cretaceous strata, and 

 reaches the modern sea in T. vitrea. The parallel line from 

 T. sacculus to T. grandis, and the limited occurrences related to 

 T. obovata, might be fairly joined into the main stream as ordinary 

 modifications by descent; but T. fimbria recurring as to type in 

 T. australis, T. cardium and T. coarctata, sporadic terms of short 

 period, require additional suppositions. 



Dd 



