FROM TANGANYIKA AND KENYA 139 



with diameter approximately equal to or slightly less than height and with narrow, 

 deep umbilicus. Whorls with slightly concave outer face, which is steeply and some- 

 what variably inclined, and a broad ramp, varying from feebly concave to feebly con- 

 vex, which forms an angle averaging about 45 ° with shell axis. Whorl shoulder 

 formed by rounded spiral cord bearing selenizone. Base feebly convex, its periphery 

 formed by second rounded cord which is almost of the same strength as the first and 

 is just exposed in places on the spire whorls. Ornament of ramp, whorl outer face 

 and base consisting of numerous spiral cords and threads of unequal strength. 

 (Collabral threads, if originally present, have been obliterated by erosion in the 

 specimens examined.) 



Holotype and paratypes. Nos. GG.10306 and GG.10307-08 respectively, three 

 specimens in all. 



Localities and horizon. At three points along the Mandawa-Namakongoro 

 stream, Mandawa-Mahokondo area, Tanganyika ; Middle-Upper Kimmeridgian. 



Remarks. Its large size distinguishes this species from any Jurassic Bathroto- 

 maria described previously. The English Upper Oxfordian and Kimmeridgian 

 species B. reticulata (J. Sowerby) (1821a : 128, pi. 272, fig. 2), which attains a dia- 

 meter of 90 mm., has not such a distinct carina at the periphery of its base and its 

 spiral ornament is rather more delicate. B. solodurina (Thurmann & Etallon) (1861 : 

 129, pi. 11, fig. 102), based on an internal mould 65 mm. in diameter from the Kim- 

 meridgian of the Swiss Jura, could possibly be a synonym of B. reticulata. B. neo- 

 solodurina (Dacque) (1905 : 141, pi. 16, figs. 5, 6), from the Kimmeridgian of Somali- 

 land, is more depressed than the new species now described. 



Superfamily PATELLACEA 



Family uncertain 



Genus PSEUDORHYTIDOPILUS Cox i960 (ex Haber, nom. nud.) 



Pseudorhytidopilus lonjiensis sp. nov. 

 PI. 22, figs. 3«, b 



Diagnosis. Outline broadly elliptical, rather flattened anteriorly and posteriorly ; 

 moderately large (length of holotype c. 33 mm., breadth c. 28 mm.), well elevated 

 (height of holotype c. 16 mm.), with apex situated at about anterior quarter of length 

 and directed anteriorly. Ornament consisting of conspicuous concentric growth- 

 undulations, about 1 mm. apart. 



Holotype. No. GG.10312. The only specimen. 



Locality and horizon. Along Lonji-Runjo stream at a point x\ miles W. of 

 Mandawa, Tanganyika ; Callovian. 



