FROM TANGANYIKA AND KENYA 75 



Trigonia kidugalloensis sp. nov. 

 PL 11, figs. 3<z, b, c 



Holotype and paratype. Holotype, no. LL.35105 ; one paratype, no. LL. 

 35106. Both ex B.P. Coll. 



Diagnosis. Small (length of holotype, when complete, c. 17 mm.), rather 

 strongly inflated, length and height nearly equal, umbones not prominent ; curva- 

 ture of marginal carina very feeble ; posterior area moderately broad, concave 

 transversely and forming a relatively wide angle with the flank ; ventral margin 

 apparently evenly convex. Flank ornamented with relatively narrow and numer- 

 ous, evenly curved, round-topped concentric ribs separated by intervals of about 

 the same width ; number of ribs on each valve of holotype 27. Ribs end a short 

 distance from the prominent, serrated marginal carina, which is thus bordered by an 

 ante-carinal groove, slightly wider in left valve than in right. The area has no 

 marked median carina or groove, but bears 6-7 nodose radial threads, and the es- 

 cutcheon carina is also nodose. 



Locality and horizon, i^ miles N.N.W. of Kidugallo, Tanganyika ; Bajocian. 



Remarks. This form resembles the European Bajocian species T. hemisphaerica 

 Lycett (re-described Lycett 1877 : 174, pi. 31, figs. 4-8 ; pi. 33, figs. 4-6 (var. gre- 

 garia)) in the closeness of the spacing of its concentric ribs, but it is less elongate and 

 more strongly inflated, and has a more distinct ante-carinal groove, especially on the 

 left valve. The broader ante-carinal groove and less prominent umbo distinguish 

 the new species from T. hemisphaerica race asiatica Douville (1916 : 29, pi. 4, fig. 9), 

 from the Bajocian of Sinai. In the French Bajocian species T. gadoisi Cossmann 

 (1912 : 8, pi. 1, figs. 6-8) the concentric ribs are still more closely arranged. 



Trigonia kenti sp. nov. 

 PI. 11, figs. 4a, b, c 



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

 Limited. 



Holotype and paratype. Holotvpe, no. LL. 35107 ; one paratype, no. LL. 

 35108. Both ex B.P. Coll. 



Diagnosis. Small (length of holotype 22 mm.), moderately inflated, length 

 slightly exceeding height, umbones moderately prominent and acute ; ventral 

 margin tending to be subangular in middle and slightly sinuate posteriorly ; posterior 

 area rather narrow, forming relatively low angle with flank. Flank ornamented 

 with rather angular concentric ribs which are curved irregularly in places and are 

 moderately wide-spaced (about 2 mm. apart) until a relatively late growth-stage, but 

 become crowded together near ventral margin. The ribs extend in both valves al- 

 most to the sharp and not strongly nodose marginal carina, the ante-carinal depres- 

 sion being very narrow. Posterior area feebly convex, with a median rib which is most 

 conspicuous in earlier stages of growth and with about four very irregularly spaced 



