130 JURASSIC BIVALVIA AND GASTROPODA 



1923. Goniomeris dilatata (Phillips ); Lissajous : 195, pi. 32, figs. 2-5. 

 1948. Osteomya dilata (Phillips) ; Cox & Arkell : 45. 



Material. Two specimens (nos. LL.i 1566-7). 



Locality and horizon. Kidugallo Station, Central Railway, Tanganyika. 

 Bajocian, Station Beds. 



Remarks. Although distorted, the specimens now recorded are unmistakable 

 examples of this species. Its range in Europe is from Bajocian to Callovian. It 

 has been recorded from the Bajocian of Madagascar, but not from East Africa pre- 

 viously. 



Family MYOPHOLADIDAE Cox 1964 



Genus MYOPHOLAS Douville 1907 



Myopholas manderaensis sp. nov. 

 PI. 19, fig. 20 



i960. Myopholas sp. nov. : Joubert, pi. 11, fig. 10. 



Diagnosis. Rather small for the genus, elongate-ovate, with the length (31 mm. 

 in the holotype) about z\ times the height (12 mm.). Inflation only moderate, but 

 possibly diminished in the course of fossilization. Umbo very broadly rounded, 

 placed at about the anterior third of the length, and not protruding above the postero- 

 dorsal margin, which slopes gradually towards the narrowly rounded posterior extre- 

 mity. Ventral margin with a broad and very shallow median sulcus. Ornament of 

 anterior two-thirds of surface consisting of 23 narrow radial ribs, the most anterior 

 three of which are separated by relatively broad intervals and the remainder by much 

 narrower ones. The most posterior of these ribs stands out slightly more prominent- 

 ly than the others ; the posterior third of the surface, lying beyond it, bears a few 

 ribs which are just visible in the earlier growth-stages and then fade away partly or 

 completely, leaving the surface almost smooth. 



Holotype. No. L. 92271, the external mould of a right valve. There are also 

 two very imperfect specimens. 



Locality and horizon. Matasafara, 15 miles W. of Mandera, N.E. Kenya ; 

 uppermost Jurassic, Gudediye Beds. 



Remarks. The virtual absence of ribbing on the posterior third of the surface 

 distinguishes this species from the European Upper Jurassic forms Myopholas mul- 

 ticostata (Agassiz) and M. percostata Douville (Douville, 1907b, pi. 2, figs. 6, 7 and 

 figs. 4, 5 respectively) and is more suggestive of the Neocomian shell M. semicostata 

 (Agassiz) (Douville, 19076, pi. 2, fig. 8), which, however, has fewer costae on the 

 anterior part of its surface. 



