76 JURASSIC BIVALVIA AND GASTROPODA 



radial threads. Escutcheon carina apparently weakly serrated (but eroded in 

 available specimens). 



Locality and horizon. 6 miles N.W. of Kidugallo, Tanganyika ; Bajocian. 



Remarks. The crowding together of the concentric ribs near the ventral margin 

 suggests that the two specimens studied, although small, are full-grown representa- 

 tives of their species. This feature, the irregular curvature of the ribs in places, and 

 the very narrow ante-carinal depression distinguish this species from T. costata 

 Parkinson. 



Trigonia cf. brevicostata Kitchin 

 PI. ii, fig. 7 



1903. Cf. Trigonia brevicostata Kitchin : 23, pi. 2, figs. 4, 5. 



J 939- Cf. Trigonia brevicostata Kitchin ; Stefanini : 224, pi. 24, figs. 11, 12. 



1952. Cf. Trigonia brevicostata Kitchin ; Cox : 112. 



Material. Four imperfect specimens. 



Locality and horizon, i mile N. of Asaharbito, N.E. Kenya ; Bathonian [? or 

 Callovian], Asaharbito Beds. 



Remarks. The specimens are internal and external moulds of the original shells, 

 the largest of which was originally almost 30 mm. long although the others are much 

 smaller. The ornament consists of well separated, coarse concentric ribs which 

 swing down to some extent and swell out at their posterior end ; they are separated 

 from the marginal carina by a well-marked ante-carinal depression, which appears to 

 be a little wider in the left valve than in the right. The posterior area bears relative- 

 ly coarse radial threads. These specimens differ from typical examples of T. brevi- 

 costata in their slightly coarser ribbing (possibly due to their state of preservation) 

 and in the tendency of the ribs to swing down posteriorly, but it is quite possible that 

 they belong to that species. T. brevicostata occurs typically in the Callovian of Cutch, 

 India, and has been recorded by Stefanini from beds in southern Somalia which seem 

 to be approximately Callovian in age. 



Trigonia elongata J. de C. Sowerby 

 PI. 11, fig. 8 



1823a. Trigonia elongata J. de C. Sowerby : 39, pi. 431. 



1903. Trigonia chariensis Kitchin : 18, pi. 1, fig. 4 ; pi. 2, fig. 1. 



1952. Trigonia elongata Sowerby ; Cox : 109, pi. 12, figs. 3, 4, 7. 



Material. One specimen (no. LL. 35109), ex B.P. Coll. 



Locality and horizon. About i\ miles W. of Mandawa, Tanganyika ; Callo- 

 vian (?). 



Remarks. This specimen does not seem distinguishable from English examples 

 of T. elongata, a species discussed by the present writer in the above-cited work, in 

 which specimens from the Callovian of Cutch, India, are described. In England its 

 range extends from the Bathonian to the Oxfordian. 



