98 JURASSIC BIVALVIA AND GASTROPODA 



Golberobe Beds. 17 miles S. of Rahmu, N.E. Kenya ; Upper Oxfordian, Seir 

 Limestones. 3 miles N.E. of Melka Dakacha, N.E. Kenya ; Upper Kimmeridgian, 

 Dakacha Limestones. Just W. of Mabokweni, 4 miles N.W. of Tanga, Tanganyika ; 

 Kimmeridgian. 



Remarks. This species, like M. aequalis, from which it scarcely differs, is 

 characterized by its rather elongate outline and by the irregularity of its concentric 

 ridges, which very commonly are undulating in places. 



Family FIMBRIIDAE Nicol 1950 



Genus FIMBRIA Mergele von Muhlfeld 181 1 



Fimbria kidugalloensis sp. nov. 

 PI. 16, figs. la, b 



Diagnosis. Shell of small-medium size (length 32 mm.), elongate, rather weakly 

 inflated. Umbones subangular, slightly anterior to median, protruding above 

 postero-dorsal outline, which is straight, sloping gently to low posterior extremity 

 of shell. Ventral margin of very feeble convexity ; antero-dorsal outline well 

 excavated ; anterior margin evenly rounded. Ornament consisting of closely and 

 rather unevenly spaced, thin concentric ridges, typically about 0-4 mm. apart in 

 later growth-stages ; many intervals between them bear one or more weak concentric 

 threads, together with traces of radial threads. 



Holotype. No. L. 54103. The only specimen. 



Locality and horizon. i£ miles E. of Kidugallo Station, Central Railway, 

 Tanganyika ; Bajocian, Station Beds. 



Remarks. The genus Fimbria is rare in the Bajocian. The species now described 

 is characterized by the fineness and close spacing of its concentric ridges. F. aspera 

 (Lycett) (1850 : 423, pi. 11, fig. 7), from the English Inferior Oolite, is much more 

 coarsely ornamented. The Kimmeridgian species F. formosa (Contejean) 

 (i860 : 275, pi. 13, figs. 1-3) has equally fine concentric ornament but is less elongate. 



Fimbria sp. " A " 

 PI. 15, fig. 6 



Material. Several specimens. 



Localities and horizons. Hills S. of Rahmu-Melka Murri road at localities 11 

 miles and 13 miles W. of Rahmu, N.E. Kenya ; Callovian, Rukesa Shales. Hills S. 

 of Rahmu-Melka Murri road at locality 9 miles W. of Rahmu ; also Muddo Erri, 

 N.E. Kenya ; Callovian [?-Lower Oxfordian], Muddo Erri Limestones. 



Remarks. Two species of Fimbria which occur in the Rukesa Shales and Muddo 

 Erri Limestones are represented in the material studied only by specimens which are 

 incomplete, much eroded, or in the form of internal moulds. The largest specimen 



