FROM TANGANYIKA AND KENYA 73 



Rahmu, N.E. Kenya ; Callovian, Rukesa Shales. Kulong, 2 miles S.W. of Muddo 

 Erri, also top of hills S. of Rahmu-Melka Murri road, 10 miles W. of Rahmu, N.E. 

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

 Central Railway, and 2 km. to the east, Tanganyika ; Callovian. 



Remarks. The specimens now recorded fall within the range of variation of L. 

 alimena as described (Cox 1952) from the Callovian and Oxfordian of Cutch, India. 

 It is difficult to define any difference between this species and L. ancliffensis Cox & 

 Arkell (1948 : 20), from the Bathonian, so far as the general form of the shell is 

 concerned, but L. ancliffensis does not exceed 11 mm. in height whereas L. alimena 

 commonly attains a much larger size. Certainly the numerous small specimens in 

 an oyster bed of which a fragment was figured by Joubert (i960) could not be sepa- 

 rated from L. ancliffensis, but other specimens from the same formation (the Rukesa 

 Shales) are larger. The radial ribs present in many English specimens referred to 

 this species and described by Arkell (1934&) have not been observed in specimens 

 from Cutch or from East Africa. 



Genus GRYPHAEA Lamarck 1801 



Gryphaea hennigi Dietrich 

 PI. 11, figs, ia, b 



1900. Gryphaea lobata Cjuenstedt ; Miiller : 521, pi. 16, figs. 6, 6a. 



1925. Gryphaea hennigi Dietrich : 6, pi. 2, fig. 4. 



1952. Gryphaea hennigi Dietrich ; Cox : 83, pi. 8, figs. 7(F), 8, ga-c. 



Material. Three left valves (nos. LL. 16848-50). 



Locality and horizon. Look-out hill opposite Kingura village, north of Wami 

 river, Tanganyika ; Upper Oxfordian. 



Remarks. The most notable feature of these specimens is the protruding lobe- 

 like antero-ventral region, and in one specimen the growth-rugae show that this was 

 separated from the rest of the valve by a broad sinus of the ventral margin. The 

 specimens are broken away posteriorly, but the largest appears from the growth- 

 rugae to have had a rather similar postero-ventral lobe. They appear to belong to 

 Gryphaea hennigi, which, according to Aitken (1961 : 25) is abundant in the Lower 

 Kimmeridgian Septarian Marl of the Mandawa-Mahokondo anticline. They are also 

 extremely close to G. moondanensis Cox (1952 : 87, pi. 9, figs. 4, 7, 8), a species from 

 the Tithonian of Cutch, north-western India, in which an antero-ventral lobe is a 

 conspicuous feature. 



Genus EXOGYRA Say 1820 



Exogyra nana (J. Sowerby) 

 Pi. 11, figs. 5, 6a, b 



1822a. Gryphaea nana J. Sowerby : 114, pi. 383, fig. 3. 



1872. Ostrea bruntrutana Thurmann ; de Loriol : 399, pi. 24, figs. 7-18. 



1929. Exogyra nana (J. Sowerby) ; Weir : 20, pi. 1, figs. 11-13. 



