30 JURASSIC BIVALVIA AND GASTROPODA 



Holotype and paratypes. Nos. LL.35086 and LL.35087-88 respectively, three 

 specimens in all, ex B.P. Coll. 



Locality and horizon. Lihimaliao creek, at a point near Mbaru creek, Mand- 

 awa area, Tanganyika ; Bajocian (?), Pindiro Shales. 



Remarks. The variability is illustrated by the following measurements of the 

 holotype and of the better preserved paratype. Holotype : length 33-3 mm., height 

 17-0 mm., inflation 12-5 mm. Paratype : length 32-5 mm., height 18-2 mm., 

 inflation 13-5 mm. 



Parallelodon elongatus (J. de C. Sowerby) (1824a: 67, pi. 447, fig. 1), a widespread 

 European Bajocian species, and P. buckmani (Richardson) (1843 : 504, text-fig. 243), 

 Lower Lias of England, are more elongate, less compressed postero-dorsally, and 

 without the wing-like extension of the hinge-margin. 



Genus GRAMMATODON Meek & Hayden i860 

 Grammatodon kenyanus sp. nov. 

 PI. 2, figs. la, b, c, 2a, b 



Diagnosis. Small (length of largest specimen 15 mm.), rectangularly ovate, not 

 much elongated (height two-thirds of length), well inflated, most so just posterior to 

 middle of shell. Umbones at about anterior two-fifths of length, broadly rounded 

 except for a slight median depression, projecting slightly above hinge-margin. 

 Posterior margin nearly straight, meeting hinge-margin in a fairly well-marked, 

 slightly obtuse angle. Posterior area somewhat compressed dorsally, not separated 

 from flank by a carina. Ornament consisting of concentric ribs which become 

 irregular in later growth-stages ; radial threads, traces of which are seen in places, 

 may have been present on the whole surface, but, if so, have been largely removed 

 by erosion in the available specimens. 



Holotype and paratypes. Nos. LL. 35006 and LL. 35007-09 respectively, four 

 specimens in all. 



Locality and horizon. Didimtu hill, 2 miles S. of Bur Mayo, N.E. Kenya ; 

 Upper Lias, Toarcian, Didimtu Beds. 



Remarks. As the hinge-structure cannot be observed, it is not certain that this 

 species belongs to Grammatodon rather than to Cucullaea, but it is included in the 

 former genus on account of its small size. It is less elongate but has a relatively 

 longer hinge-margin than G. muensterii (Zieten) (1833 : 75, pi. 56, figs, ya-c), Middle 

 [?-Upper] Lias of Europe, and also differs in the presence of the concentric ribs. 



Grammatodon sublaevigatus (Zieten) 

 PI. 2, fig. 7 



1S33. Cucullaea sublaevigata Hartmann [MS.] ; Zieten : 75, pi. 56, figs. $a-c. 



1837. Area cucullata Miinster [MS.] ; Goldfuss : 148, pi. 123, figs. ya-c. 



1837. Area concinna (Phillips) ; Goldfuss : 148, pi. 123, figs. 6a, b (non Cucullaea concinna 



Phillips). 

 [952. Grammatodon cf. bathonicus Cox & Arkell ; A vers : **■ 



