FROM TANGANYIKA AND KENYA 133 



1863. Ceromya concentrica (Sowerby) ; Lycett, pi. 36, fig. 5. 

 1948. Ceratomya concentrica (Sowerby) ; Cox & Arkell : 41. 

 i960. Ceratomya concentrica (Sowerby) ; Joubert, pi. 10, figs, ga, b. 



Material. About four specimens. 



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

 Rukesa Shales. Kulong, 2 miles S.W. of Muddo Erri, N.E. Kenya ; Callovian [?- 

 Lower Oxfordian], Muddo Erri Limestones. 



Remarks. In the specimens on which the ornament is best preserved the con- 

 centric ribs are numerous and closely arranged, as in specimens from the Great Oolite 

 of England. There is also an imperfect specimen from the Bajocian of Kidugallo, 

 Tanganyika, which seems to be very similar to C. concentrica but is more coarsely 

 ribbed. This may perhaps belong to the related species C. bajociana (d'Orbigny). 



Ceratomya pittieri (de Loriol) 

 PI. 21, fig. 4 



1883. Ceromya pittieri de Loriol : 25, pi. 6, figs. 3, 4. 



1910. Ceromya concentrica (Sow.) ; Dacque : 33, pi. 5, fig. 6 only (non Sowerby sp.). 



Material. One specimen (no. LL. 35160), ex B.P. Coll. 



Locality and horizon. Magindu, Central Railway, Tanganyika ; Callovian. 



Remarks. This specimen, which is 94 mm. long, is a well elongated Ceratomya 

 with an almost terminal, only slightly protruding umbo which is strongly incoiled to 

 the beak. A slight radial depression of the flank appears at mid-growth and termin- 

 ates at the ventral margin near its anterior end. The ventral margin diverges 

 gradually from the hinge-margin in a posterior direction. The surface ribs, although 

 partly obliterated by erosion in places, can be seen to be regularly concentric and 

 fairly closely arranged. 



Except for the presence of the radial depression, the shape of the shell agrees with 

 de Loriol's figures of C. pittieri, the type specimens of which came from the Callovian 

 Mytilus Beds of the Alps of Vaud, Switzerland. The Abyssinian Kimmeridgian (?) 

 species C. paucilirata (Blanford), especially as figured by Futterer (1897, pi. 22, 

 fig. 1) also resembles the present specimen in shape, but its concentric ribs are not so 

 closely arranged. These forms are very close to de Loriol's (1872, pi. 12, fig. 13) 

 " var. cylindrica " of C. excentrica, an Upper Oxfordian-Kimmeridgian species highly 

 variable in form and ornament. In view of the Callovian age of the specimen now 

 recorded, however, it seems most satisfactory to identify it as C. pittieri. 



Ceratomya wimmisensis (Gillieron) 



1883. Ceromya concentrica (Sowerby) ; de Loriol : 18, pi. 5, figs. 1-5 {non J. de C. Sowerby 



sp.). 

 1886. Ceromya wimmisensis Gillieron : 141. 



1918. Ceromya wimmisensis Gillieron ; Gerber : 12, pi. 1, figs. 3-6. 

 1929. Ceratomya wimmisensis (Gillieron) ; Weir : 31, pi. 3, fig. 2. 



