ii4 JURASSIC BIVALVIA AND GASTROPODA 



height about four-fifths of length, inflation moderate. Umbo broadly rounded, 

 incurved to the moderately prosogyrous beak, which is situated at the anterior 

 quarter of the length of the shell ; outline of umbo continuous with the evenly 

 convex postero-dorsal outline, which slopes at a fairly steep angle to the low, abruptly 

 rounded posterior extremity. Ventral margin feebly convex, continuous with 

 strongly and evenly convex anterior margin ; antero-dorsal outline well excavated. 

 Lunule shallow, not bordered ; escutcheon ridge as well as ridge running diagonally 

 from umbo to postero-ventral corner weakly defined. Surface ornamented in 

 later growth-stages with narrow, irregular concentric undulations. 



Hinge-teeth of right valve consisting of elongated outer posterior cardinal (4^) 

 adjacent to nymph, a strong, well elongated inner posterior cardinal (2 of Douville\ 

 2b 2 of Casey) sloping back from the beak, an equally strong and similarly well elon- 

 gated anterior cardinal (2b 1 of Casey) diverging at obtuse angle from inner posterior 

 cardinal, and an anterior lateral Aii, which is separated from the anterior cardinal 

 by a distinct constriction. 



Holotype and paratypes. Holotype, no. LL.35144 ; two paratypes, including 

 no. LL.35145 ; all ex B.P. Coll. 



Locality and horizon. Magole, 5 miles N.W. of Kidugallo, Tanganyika ; Bajo- 

 cian. 



Remarks. As the dentition of the right valve is unknown it is not possible to 

 assign this species to any genus with complete confidence. The hinge of the left 

 valve agrees with that of the type-species of Eotrapezium, Mesodesma germari Dun- 

 ker, from the Lower Lias, as figured by Boehm (1901 : 238, fig. 19) and by Douville 

 (1913 : 455, fig. 38), in the elongation and broad divergence of the two inner cardinal 

 teeth, but the anterior of these passes without any interruption into the anterior 

 lateral in E. germari and in two other species of Eotrapezium figured by Douville 

 (1913, figs. 40, 42), whereas it is separated from it by a distinct constriction in the 

 species now described. The dentition of the left valve of this species also bears some 

 resemblance to that of Anisocardia (Antiquicyprina) loweana (Morris & Lycett), 

 from the English Bathonian, as figured by Casey (1952 : 151, fig. 49), but the two 

 inner cardinal teeth are much more elongated than in the species in question. 



Family NEOMIODONTIDAE Casey 1955 



Genus EOMIODON Cox 1935 



Eomiodon baroni (Newton) 

 PI. 18, fig. 11 



1889. Astarte? baroni Newton : 336, pi. 14, figs. 9-1 1. 



1936. Astarte baroni Newton ; Besairie : 121, pi. 7, figs. i, 2. 



Material. Several specimens. 



Localities and horizons. Quarries N.N.E. of Ngerengere, Central Railway, 

 Tanganyika ; Bajocian (?). 6 miles N.W. of Kidugallo, Tanganyika ; Bajocian 

 (B.P. Coll.). 



