FROM TANGANYIKA AND KENYA 129 



Genus GONIOMYA Agassiz 1841 



Goniomya trapezicostata (Pusch) 

 PI. 21, figs. 2, 3 



1836. Lutraria trapezicostata Pusch : 80, pi. 8, figs. loa-c. 



1840. Lysianassa ornata Munster ; Goldfuss : 264, pi. 154, fig. 12. 



1842. Goniomya inflata Agassiz : 20, pi. 1, fig. 15. 



1852. Pholadomya trapezina Buvignier : 8, pi. 8, figs. 14-18. 



1900. Goniomya cf. trapezina (Buvignier) ; Miiller : 536, pi. 18, figs. 2, 2a. 



1924. Goniomya trapezicostata (Pusch) ; Cossmann : 51, pi. 7, figs, g, 10. 



Material. Two specimens (nos. L. 54080, LL.35I57), the second ex B.P. Coll. 



Localities and horizons. i£ miles E. of Kidugallo Station, Central Railway, 

 Tanganyika. Bajocian. £ mile N.W. of bridge over Mkulumuzi river, 2 miles W. of 

 Tanga, Tanganyika ; Callovian. 



Remarks. In this species the steep oblique ribs on the anterior and posterior 

 parts of the surface are separated in all stages of growth by a horizontal rib, instead 

 of meeting to form a series of V's, as in most species of the genus. In the specimen of 

 Bajocian age now recorded the intervening horizontal ribs are shorter than in the 

 Callovian specimen, which agrees better with the typical G. trapezicostata. The 

 difference, however, does not seem important enough to justify its specific separation. 

 In Europe G. trapezicostata occurs in the Callovian and Oxfordian. 



Goniomya literata (J. Sowerby) 



1819a. Mya? literata J. Sowerby : 45, pi. 224, fig. 1. 



1819a. Mya v. scripta J. Sowerby : 46, pi. 224, figs. 2-5. 



1935a. Goniomya literata (Sowerby) ; Arkell : 344, pi. 48, figs. 1-7. 



1939. Goniomya literata (Sowerby) ; Stefanini : 254, pi. 26, figs. 3a, b. 



Material. One specimen (no. LL. 16846). 



Locality and horizon. Scarp face, eastern margin of Makoko plain, Bagamoyo 

 hinterland, Tanganyika ; Oxfordian. 



Remarks. In this specimen the convergent oblique ribs almost die out at mid- 

 growth, particularly on the posterior part of the surface. In this respect the speci- 

 men agrees with G. marginata Agassiz, as interpreted by de Loriol (1872 : 187, pi. 12, 

 figs. 3, 4) and Boden (191 1 : 58, pi. 6, figs. 2, 2a), although it is to be noted that 

 Agassiz's (1842, pi. 1, figs. 12-14 ; pi. ic, fig. 15) original figures of G. marginata do 

 not show this fading away of the ribs. Arkell (1935a : 346) was of the opinion that 

 G. marginata, even as interpreted by the authors cited, is inseparable from G. literata. 



Genus OSTEOMYA Moesch, 1874 

 Osteomya dilata (Phillips) 



1829. Mya dilata Phillips : 155, pi. 11, fig. 4. 



1855. Myacites dilatus (Phillips) ; Morris & Lycett : 114, pi. 10, figs. 5a, b. 



