42 JURASSIC BIVALVIA AND GASTROPODA 



Remarks. The differences between this species and B. {A.) subpectinatus (d'Or- 

 bignv) { = pectinatus (J. Sowerby)) were discussed by me in the work cited above. 

 The specimens now recorded, including those from the Kimmeridgian, agree with 

 B. (A.) laitmairensis in their rounded postero-ventral margin and in the absence of a 

 definite ridge running from the umbo to the posterior end of this margin. This 

 species occurs most commonly in the Callovian, but Arkell has recorded its occurrence 

 in the English Oxfordian. It has not been recorded previously from the Kimmerid- 

 gian. The true B. (A.) subpectinatus has been recorded from Tendaguru by Dietrich 

 ( I 933 : 7 2 - P 1 - 2 . n g- 47). but is not represented in the collections from that locality 

 in the British Museum (Natural History). 



Superfamily PTERIACEA 

 Family PTERIIDAE Gray 1847 



Genus PTERIA Scopoli 1777 



Pteria tanganyicensis sp. nov. 



PL 4( fig. 4 



Diagnosis. Large (original length at least 9 cm.), well inflated, obliquely elon- 

 gate, with a rather narrow body which has a slight sigmoidal curvature. Anterior 

 wing large, acute, not compressed ; posterior wing more compressed and differentia- 

 ted from the body than the anterior one, appearing (from its earlier growth lines) to 

 have had an acutely pointed tip (it is broken away distally in the holotype). Sur- 

 face of shell without radial ornament. 



Holotype. No. LL. 16793, a right valve damaged posteriorly. The only specimen. 



Locality and horizon. Usigiwa river, 6 miles W.S.W. of Kiwangwa, Baga- 

 moyo hinterland, Tanganyika ; Upper Oxfordian. 



Remarks. The cardinal area is not seen in the holotype, so that the number of 

 ligamental pits cannot be ascertained, but the species is referred to Pteria as its 

 general form is more suggestive of that genus than of any representatives of the family 

 Bakevelliidae. In size and shape it much resembles Avicula struckmanni de Loriol 

 (1875 : 164, pi. 20, fig. 1), from the Kimmeridgian of France, but it differs in the 

 much larger size of its anterior auricle. No comparable form has been recorded 

 previously from East Africa. 



Family BAKEVELLIIDAE King 1850 



Genus BAKEVELLIA King 1848 



Bakevellia iraonensis (Newton) 



[80,5, Gervillia iraonensis Newton : So, pi. 2, figs. 8, 9. 



Material. Four specimens (nos. LL. 7224-27). 



Locality and horizon. Quarries N.N.E. of Ngerengere, Central Railway, 

 Tanganyika ; Bajocian (?). 



