FROM TANGANYIKA AND KENYA 85 



Bajocian of Europe, but is more finely ribbed and less rectangular in outline. A. 

 depressa Goldfuss, a Bajocian species well figured by Cossmann (1913a : 9, pi. 3, 

 figs. 18-27), is more trigonal in outline. A. gillieroni Mayer (1875 : 234, pi. 10, 

 fig. 4), Upper Lias of Switzerland, is a larger form with a more strongly prosogyrous 

 umbo. 



Astarte sp. 



PL 12, figs. 15a, b 



Material. One specimen (no. LL. 35043), defective postero-ventrally. 



Locality and horizon. Didimtu hill, 2 miles S. of Bur Mayo, N.E. Kenya ; 

 Upper Lias, Toarcian, Didimtu Beds. 



Description. Small (length when complete c. 7-5 mm.), suborbicular, with a tri- 

 gonal tendency, inequilateral ; height and length almost equal, beaks at anterior 

 fifth of length ; inflation moderately strong. Umbo rather broadly rounded, well 

 incurved ; postero-dorsal outline moderately convex and sloping, forming a rounded- 

 off, obtuse angle with the low, almost straight, subvertical posterior margin ; ventral 

 margin rather strongly convex ; antero-dorsal outline very feebly concave, steeply 

 sloping ; anterior margin low. Lunule (rather obscured in this single specimen) 

 moderately impressed ; presence of escutcheon doubtful. Ornament consisting of 

 fine, equal concentric riblets. 



Remarks. This form is more gibbose than A. subminima and has rather stronger 

 concentric riblets, but the single specimen seems too imperfect to serve as the type 

 of a new species. 



Astarte kenti sp. nov. 

 PL 12, figs. 6a, b, ya, b 



Specific name. After Dr. P. E. Kent, of the British Petroleum Co., Ltd. 



Diagnosis. Small (maximum length c. 15 mm.), trigonally ovate, height two- 

 thirds to three-quarters of length ; inequilateral, beaks from anterior quarter to 

 third of length ; inflation weak. Umbones obtusely angular, not incurved, mode- 

 rately prominent ; postero-dorsal outline convex, gently sloping, antero-dorsal 

 outline almost straight, steeply sloping ; lunule absent or ill-defined ; escutcheon, if 

 distinguishable, narrow and limited by ill-defined umbonal ridges. Posterior margin 

 feebly convex, varying in height and inclination ; ventral margin flat to feebly con- 

 vex. Early growth-stages ornamented with regular, close-spaced concentric ridges, 

 later stages with rather irregular concentric undulations and rugae. Valve margins 

 denticulate internally. 



Holotype and paratypes. Holotype, no. LL.35113 ; about 18 paratypes. 



Locality and horizon. Near site of Mandawa well no. 1, Tanganyika ; Bajo- 

 cian^). 



Remarks. The most closely described Bajocian species is Astarte hauthali Wetzel 

 (1911 : 249, pi. 20, figs. 19, 20), which is slightly more rectangular. 



