9 o JURASSIC BIVALVIA AND GASTROPODA 



Astarte mandawaensis sp. nov. 

 PI. 14, figs. 6a, b 



Diagnosis. Of medium size (length of holotype 38 mm.), ovate, rather strongly 

 inequilateral, length exceeding height, beak at anterior third of length ; shell well 

 inflated for the genus. Umbo obtusely angular, depressed, slightly incurved to 

 prosogyrous beak. Postero-dorsal outline rather strongly convex, level with umbo 

 anteriorly, down-curved posteriorly, where it forms an obtuse angle with the some- 

 what flattened posterior margin ; ventral and anterior margins forming an uninter- 

 rupted curve of strong convexity ; antero-dorsal outline strongly concave. Lunule 

 broad, flattened and deep, bordered by well-defined ridge ; escutcheon narrow. 

 Ornament of irregular concentric undulations which are broad and relatively few on 

 anterior two-thirds of surface but increase in number by intercalation or bifurcation 

 on posterior part, where they are consequently of diminished width. 



Anterior cardinal tooth of left valve stout and prominent, sloping back from beak 

 and separated by narrow space from lunular margin ; posterior cardinal tooth 

 elongate, slightly curved, forming very acute angle with ligamental nymph. 



Holotype. No. LL.35121, ex B.P. Coll. The only specimen. 



Locality and horizon. Lonji creek, W. of Mandawa, Tanganyika ; Upper 

 Kimmeridgian. 



Remarks. Although the postero-ventral part of the holotype is broken away, 

 the well inflated, ovate form of the shell is very distinctive for an astartid, while the 

 ornament is also characteristic. It differs from the approximately contemporaneous 

 East African species A. weissermeli Dietrich, recorded below (p. 92), in its more 

 elongate outline, its broader and more unevenly arranged concentric undulations, 

 and its deep, distinctly bordered lunule. 



Astarte lonjiensis sp. nov. 

 PI. 14, fig. 1 



Diagnosis. Large (length of holotype 74 mm.) , ovate with slight trigonal tendency, 

 highly inequilateral, height six-sevenths of length ; inflation rather weak. Umbo 

 almost terminal, slightly incurved, rather sharply rounded in outline ; postero- 

 dorsal outline continuous with that of umbo, at first convex and rising very slightly 

 above level of latter, but almost straight and sloping gently downwards along greater 

 part of length ; it forms a slightly obtuse angle with the short, straight, subvertical 

 posterior margin. Antero-dorsal outline steep, slightly concave ; ventral margin 

 very strongly convex. Lunule narrow, moderately excavated ; no escutcheon. 

 Early growth-stages ornamented with regular, rather closely spaced concentric ribs, 

 which in later stages are replaced by coarse, irregular rugae. Interior not exposed. 



Holotype. No. LL.35122, ex B.P. Coll. The only specimen. 



Locality and horizon. Lonji creek, W. of Mandawa, Tanganyika ; Upper 

 Kimmeridgian. 



