66 JURASSIC BIVALVIA AND GASTROPODA 



posterior slightly the larger. Median part of valve ornamented with 13 angular 

 costae which are separated by slightly narrower, angular intervals and bear small, 

 evenly spaced nodes. Ribbed area sharply separated from anterior and posterior 

 parts of surface, which are smooth except for a few faint radial lines and growth- 

 lines. 



Holotype and paratype. Nos. LL.11514, LL.11515 respectively. 



Locality and horizon. Kindope, N.N.W. of Tendaguru, Tanganyika ; Upper 

 Kimmeridgian, Nerinella Bed. 



Remarks. A species Limatula tendagurensis Lange (1914 : 207, pi. 15, figs. 6a, b) 

 was described from the Neocomian of Tendaguru, and Dietrich (1933 : 63) has stated 

 that it ranges throughout the whole series of beds at that locality. The Jurassic 

 form now described differs, however, from Lange 's figures in its more strongly con- 

 vex anterior and posterior margins and its broader proportions. It also has fewer 

 ribs, the number mentioned by Lange being 15-17 in addition to some weaker ones 

 which extend on to the lateral parts of the surface. 



Genus CTENOSTREON Eichwald 1862 

 Ctenostreon proboscideum (J. Sowerby) 



1820a. Lima proboscidea J. Sowerby : 115, pi. 264. 



1932a. Ctenostreon proboscideum (Sowerby) ; Arkell : 145, pi. 15, fig. 3. 



1937. Ctenostreon proboscideum (Sowerby) ; Hennig : 180. 



i960. Ctenostreon proboscideum (Sowerby) ; Joubert : pi. 8, fig. 7. 



Material. One specimen (no. L.92184). 



Locality and horizon. Melka Dakacha, N.E. Kenya ; Upper Kimmeridgian, 

 Dakacha Limestones. 



Remarks. The specimen now recorded is a relatively small, ill-preserved internal 

 mould with about nine radial ribs. The species was recorded by Hennig from beds 

 thought to be Kimmeridgian in age at a locality in the Mandawa district of Tangan- 

 yika. 



Superfamily OSTREACEA 



Family OSTREIDAE Rafinesque 1815 



Genus LOPHA Roeding 1798 



Lopha costata (J. de C. Sowerby) 

 PI. 9, figs, la, b, c 



1825a. Ostrea costata J. de C. Sowerby : 143, pi. 488, fig. 3. 

 1853. Ostrea costata Sow. ; Morris & Lycett : 3, pi. 1, figs. 5, 5a. 

 1856. Ostrea costata Sow. ; Quenstedt : 497, pi. 66, figs. 43, 44. 

 1863. Ostrea costata Sow. ; Martin : 65, pi. 5, figs. 12-15. 

 1868. Ostrea costata Sow. ; Lycett, pi. 34, fig. 3. 



