36 JURASSIC BIVALVIA AND GASTROPODA 



of the ventral margin. It is much more elongate than a specimen from Tendaguru 

 recorded by Dietrich (1933 : 26, pi. 2, fig. 36) as Area (Eonavicula) cf. quadrisulcata 

 (Sow.). E.fracta (Goldfuss) (1837 : I 4 I « P L I2I > n § s - 10a > fy, from the Kimmerid- 

 gian of Germany, is similarly elongate, but the broad sinus of its ventral margin 

 occupies a more anterior position. 



Superfamily MYTILACEA 



Family MYTILIDAE Rafinesque 1815 



Genus LITHOPHAGA Roding 1797 



Lithophaga suboblonga Dietrich 



1933. Lithophaga suboblonga Dietrich : 73, pi. 7, figs. 94, 95. 



Material. Numerous crypts preserved in limestone. 



Localities and horizons. Kipande creek, Lilomba creek, Tingutitinguti creek, 

 and N.E. of Nguruwe, all near Tendaguru, Tanganyika ; Upper Kimmeridgian, 

 " Trigonia smeei " Bed. Kindope, 2 miles N.N.W. of Tendaguru, Tanganyika; 

 Upper Kimmeridgian, Nerinella Bed. 



Genus MODIOLUS Lamarck 1799 



Modiolus imbricatus (J. Sowerby) 

 PI. 3, figs. 5, 6 



1818a. Modiola imbricata J. Sowerby : 21, pi. 212, figs. 1, 3. 



1935a. Mytilus {Modiolus) imbricatus (J. Sowerby) ; Cox : 162, pi. 16, figs. 3-5. 



Material. About four specimens. 



Localities and horizons. Lihimaliao creek, at a point near Mbaru creek, 

 Mandawa area, Tanganyika ; Bajocian (?), Pindiro Shales. Tifo, 14 miles N. of 

 Wergudud, and Korkai Hammassa, 19 miles E. of Takabba, both N.E. Kenya ; 

 Oxfordian, Golberobe Beds. 



Remarks. Although from two well separated horizons, all the specimens now 

 recorded seem indistinguishable from the typical M. imbricatus. The range of this 

 species in Europe is generally accepted as from Bajocian to Callovian, and closely 

 comparable forms found in the Oxfordian and Kimmeridgian have usually been 

 identified as M. aequipiicatus (Strombeck) (M. subaequiplicatus (Roemer)). The 

 view that such forms are specifically inseparable from M. imbricatus was adopted by 

 me in 1935 when recording specimens from both the Callovian and the Oxfordian of 

 British Somaliland, and I am still convinced of its correctness. 



