FROM TANGANYIKA AND KENYA 97 



Diagnosis. Small for genus (length 17 mm.), elongate-ovate, slightly inequi- 

 lateral, height less than two-thirds of length, beaks at anterior two-fifths of length ; 

 inflation moderate for genus. Umbones very broadly rounded, well incurved to 

 slightly prosogyrous beaks, and projecting a little above antero-dorsal outline, which 

 slopes gently and meets the feebly convex posterior margin in a broad curve ; 

 ventral margin of very feebly convexity, symmetrical ; anterior margin of feeble 

 convexity, not much shorter than posterior margin ; antero-dorsal outline feebly 

 concave, scarcely sloping. Ornament consisting of irregular concentric ribs and 

 rugae. 



Holotype. No. LL. 35127, ex B.P. Coll. No other material has been examined. 



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

 cian(?). 



Remarks. This shell is even more elongate than Mactromya aequalis Agassiz 

 (1843 : 196, pi. gd, figs. 5-8), a species of Bathonian-Callovian age, and is also more 

 strongly inflated. 



Mactromya aequalis Agassiz 

 PI- 15, fig. 7 



1843. Mactromya aequalis Agassiz : 196, pi. gd, figs. 5-8. 



1912. Mactromya aequalis Agassiz ; Lissajous : 97, pi. 12, fig. 11. 



1915^. Arcomya bicorrugata Cossmann : 12, pi. 1, fig. 5 ; pi. 2, figs. 9-1 1 ; pi. 3, figs. 14-16. 



1929. Mactromya rugosa auct. ; Weir, 34, pi. 3, figs. 16, 17 {non 18) (non Roemer). 



1935a. Mactromya aequalis Agassiz ; Cox : 183, pi. 19, figs. 16, 17a, b. 



1939. Mactromya aequalis Agassiz ; Stefanini : 259, pi. 27, fig. 1. 



i960. Mactromya aequalis Agassiz ; Joubert, pi. 10, figs, ja, b. 



Material. Several specimens. 



Localities and horizons. 3! miles W. of Melka Biini, N.E. Kenya ; Callovian, 

 Rukesa Shales. 14 miles W.S.W. of Rahmu, also Muddo Erri and Kulong, 2 miles 

 S.W. of Muddo Erri, all N.E. Kenya ; Callovian [?-Lower Oxfordian], Muddo Erri 

 Limestones. 



Remarks. These poorly preserved specimens are similar to those from British 

 Somaliland which I figured in 1935. They are characterized by the irregularity of 

 their concentric ridges and corrugations. 



Mactromya quadrata (Roemer) 

 PI. 15, figs. 11a, b 



1836. Mya rugosa Roemer : 125, pi. 9, figs. 16, 17 (non Gmelin). 



1836. Mya quadrata Roemer : 126. 



1840. Lutraria concentrica Munster in Goldfuss : 258, pi. 153, figs. 5a, b. 



1843. Mactromya rugosa (Roemer) ; Agassiz : 197, pi. gc, figs. 1-23. 



1872. Lucina rugosa (Roemer) ; de Loriol : 266, pi. 16, fig. 1. 



1912. Mactromya rugosa (Roemer) ; Lissajous : 97, pi. 12, fig. 12. 



Material. Four specimens. 



Localities and horizons. Kailta, Golberobe hills, N.E. Kenya ; Oxfordian, 



