LAKE TANGANYIKA AN OLD JURASSIC SEA. 321 



Fig. 3. — Front and back view of Bathanalia Howsei (Moore), Tan- 

 ganyika. 



Fig. 3a. — Upper figure, back view of Amberlya, sp. ? from the Inferior 

 Oolite, British Museum ; lower, front view of Amberlya, sp. ? from the Lias, 

 the corresponding Jurassic forms. 



Fig. 4. — Front and back viewof Spekia zouatus (Woodward), Tanganyika. 



Fig. 4a. — Front and back vie w of N i r i d o m u s m i n u t u s, var. t u m i d u 1 u s 

 (PhilL), the corresponding Jurassic form. 



Fig. 5. — Front and backview of Limnotrochus Thorn psoni (Smith), 

 Tanganyika. 



Fig. 5a. — Front and back view of Littorina sulcata, the corresponding 

 Jurassic form. 



Fig. 6. — Back view and base of Limnotrochus Kirkii (Smith), Tan- 

 ganyika. 



Fig. 6a. — Back view and base of Xenophora (Onustus), from the Liferior 

 Oolite. 



Fig. 7.— Back view of the shell of Pyrgul ifera-humerosa (Meek), from 

 the fresh-water deposits of the upper chalk. 



