PLATE 40 



Strophonella (Amphistrophia) continens nov. 



Page 195 



1 The exterior of a dorsal valve. The ventral behind it 



2 Interior of the umbonal portion of a ventral valve, showing the outline 



of the muscle scars 



3 A ventral valve with the sharp umbonal plications retained and expos- 



ing the internal cast over the rest of the surface 



4 External cast of a ventral valve 



5 Enlargement of the surface, x 3 



6, 7 Partially exfoliated ventral valves 



8, 9 External cast and exterior of the same ventral valve 



10 Interior of a dorsal valve 



1 1 ■ A ventral valve, showing the sharp, simple umbonal plications, the 



gradual fasciculation and ultimate fine subdivision of the striae 



Strophonella continens van equiplicata nov. 



Page 196 



12 A ventral valve, showing the characteristics of the variety which are 



the protracted continuation of the simple plication peculiar to early 

 growth phases of S. continens 



13 An enlargement of the surface, showing the angular plications and 



broad grooves with their concentric lines, x 5 



Strophonella continens van equalis nov. 



Page 197 



14 External cast of a ventral valve 



15 Exterior of a ventral valve. These specimens, showing the predomi- 



nance of fasciculation over the entire surface of the shell 



Strophonella continens van senilis nov. 



Page 197 



16 External cast of the ventral valve in which the fine striation peculiar 



to senile stages of S. continens prevails over most of the shell 

 and indicates acceleration of growth 

 Grande Greve limestone ; division 2. Grande Greve, Lehuquet's 

 Cove, Indian Cove and Shiphead 



332 



