FROM TANGANYIKA AND KENYA 91 



Remarks. This species is less tumid than A. sowerbyana, has a more strongly 

 convex ventral margin, and is more closely ribbed on its umbonal region. It is less 

 orbicular in shape than A. recki Dietrich, which is abundant in the Upper 

 Jurassic at Tendaguru. 



Astarte subobovata Dietrich 

 PI. 15, %. 4 



1933. Astarte subobovata Dietrich : 40, pi. 5, figs. 68, 74 ; pi. 9, fig. 141. 



Material. One specimen (no. L. 52683). 



Locality and horizon. Maimbwi river, Tendaguru, Tanganyika ; Upper 

 Kimmeridgian, " Trigonia smeei " Bed. 



Remarks. Dietrich's two figured syntypes showing the exterior of the shell 

 (pi. 5, fig. 68 ; pi. 9, fig. 141) differ considerably in shape. A study of the figures 

 suggests, however, that the distinction between this species and the closely com- 

 parable species A. recki lies mainly in the broadness of the concentric folds on the 

 main part of the surface, which rather resemble those of a Cardinia. Other points 

 of distinction are the less strongly convex postero-dorsal margin and the stronger 

 inflation of the shell, especially in the umbonal region. On the basis of such differ- 

 ences, a single specimen in the material studied is assigned to A. subobovata. 



It is not clear why Dietrich not only commented on the similarity between this 

 species and the Lower Cretaceous species A. obovata J. de C. Sowerby but also as- 

 signed a specific name to it suggesting affinity with the form in question. In A. 

 obovata the concentric folds on the main part of the surface of the shell are of much 

 smaller amplitude than in A. subobovata and not in the least reminiscent of those of 

 a Cardinia. 



Astarte recki Dietrich 

 PI. 14, figs. 4, 5 

 1933. Astarte recki Dietrich : 40, pi. 4, fig. 60 ; pi. 5, figs. 69-71. 



Material. Several specimens. 



Localities and horizons. Several localities around Tendaguru, Tanganyika ; 

 Upper Kimmeridgian, Nerinella and " Trigonia smeei " Beds. 



Remarks. A particular characteristic of this large species is the broad convexity 

 (almost an obtuse angularity) of the anterior part of the postero-dorsal margin, which 

 rises well above the level of the beak. The length of the shell exceeds the height very 

 slightly and the anterior margin projects beyond the beak to a variable extent, but 

 usually not very much. In most specimens the posterior margin is a little flattened, 

 but in some it is convex and merges with the ventral margin in an even curve. Up 

 to a height of 25 mm. the shell bears closely and regularly spaced concentric ridges, 

 but in later growth-stages these are replaced by irregular rugae and corrugations. 

 The length of the largest specimen examined is about 90 mm. 



