78 JURASSIC BIVALVIA AND GASTROPODA 



The large series of specimens figured by Venzo (1949) as T. brevicostata Kitchin 

 and as varieties of his new species T. dainellii seem to present all gradations between 

 shells in which the flank ribs continue on to the carina, as in the specimens now 

 recorded, and shells with a smooth ante-carinal area ; this area varies in width and 

 does not always have a well-defined anterior border. In some specimens included 

 by Yenzo in the forma typica of T. dainellii (e.g. his fig. 3) some of the ribs bifurcate 

 on the carina, as in the present specimens. 



T. dainellii bears a very close resemblance to the European species which has been 

 well figured by de Loriol (1868 : 160, pi. 10, figs. 12-16 ; pi. 11, fig. 3) under the 

 name T. truncata Agassiz. The species in question has a wide range of variation 

 similar to that of T. dainellii, and some of its variants have been considered by 

 Munier-Chalmas (1882 : 498-500) to belong to distinct species to which he has as- 

 signed names. The specimens from Kenya now recorded are close to de Loriol's pi. 

 10, figs. 12, 14, re-named by Munier-Chalmas T. autissiodorensis and T. breoni 

 respectively. The type-specimens of both of these " species " are from the " Port- 

 landian " (probably Upper Kimmeridgian in the British sense) of Auxerre, Yonne, 

 France. It is possible and even probable that T. dainellii is synonymous with these 

 European forms, although perhaps not with the true T. truncata, a species founded by 

 Agassiz on ill-preserved specimens. 



Subgenus FRENGUELLIELLA Leanza 1942 



Trigonia (Frenguelliella) tealei Cox 



PI. 11, fig. 10 

 19376. Trigonia tealei Cox : 201, pi. 16, figs. 2, 3. 



Material. Several specimens, including the holotype (no. L. 541 13). 



Localities and horizons. S. of Tarawanda, 11 miles S.E. of Lugoba, Tangan- 

 yika (type-locality) ; Callovian. 2 miles E. of Magindu Station, Central Railway, 

 Tanganyika ; Callovian. Chinamba, f mile S. of Amboni quarries, Tanga, Tangan- 

 yika ; Callovian? (ex B.P. Coll.). Scarp face, eastern margin of Makoko plain, 

 Bagamoyo hinterland, Tanganyika, also Usigiwa river, 6 miles W.S.W. of Kiwanga, 

 Bagamoyo hinterland ; Oxfordian. 



Remarks. The flank ornament of this species resembles that of T. brevicostata 

 Kitchin (1903 : 23, pi. 2, figs. 4, 5), from the Callovian of Cutch, India, but the orna- 

 ment of the posterior area, radial in T. brevicostata and transverse in T. tealei, en- 

 ables the two forms to be distinguished. 



Subgenus INDOTRIGONIA Dietrich 1933 



Trigonia (Indotrigonia) smeei auct. 



1914. Trigonia smeei Sowerby ; L,ange : 225, pi. 20, figs. 8-13 ; pi. 21, figs. 1-7. 

 1933. Trigonia (Indotrigonia) smeei Sowerby ; Dietrich : 30, pi. 3, figs. 48-51, 54-56. 



