136 



JURASSIC BIVALVIA AND GASTROPODA 



19 1 2. Thracia viceliacensis d'Orb. 



1916. Thracia viceliacensis d'Orb. 



1925. Thracia viceliacensis d'Orb. 



1935a. Thracia viceliacensis d'Orb. 



*939- Thracia viceliacensis d'Orb. 



Lissajous : 102, pi. 12, fig. 20. 

 Douville : 56, pi. 6, fig. 9. 

 de la Bouillerie : 89, pi. 9, fig. 4. 

 Cox : 190, pi. 20, fig. 5. 

 Stefanini : 266, pi. 27, figs. 9, 10. 



Material. One specimen (no. LL.35162), ex B.P. Coll. 



Locality and horizon. Lonji creek, W. of Mandawa, Tanganyika ; Callovian. 



Remarks. This specimen, which is 36 mm. long, is in every way typical of T. 

 viceliacensis, a species characterized by its prominent, obtusely angular, submedian 

 umbones and not very elongated form. The species was originally described from the 

 Bathonian of France and has been recorded from beds attributed to that stage in 

 Algeria and Sinai as well as in Europe. In British Somaliland, however, it has been 

 found in beds regarded as Callovian. A specimen from beds of doubtful but possibly 

 post-Callovian age at Dakatch, Italian Somaliland, attributed by Weir (1929 : 34, 

 pi. 3, fig. 19) to T. viceliacensis is not so tall and trigonal as typical specimens of the 

 species and may belong to a distinct form. 



Superfamily POROMYACEA 



Family CUSPID ARIIDAE Dall 1886 



Genus CUSPID ARIA Nardo 1840 



Cuspidaria ayersi sp. no v. 



PL 21, figs. 6a, b, ya, b 



Specific name. After Mr. F. M. Ayers, of the Geological Survey of Kenya. 



Diagnosis. Shell of small-medium size (length of holotype 10-3 mm.), slightly 

 longer than high, subalate posteriorly. Left (and only known) valve strongly in- 

 flated, with very prominent and narrowly rounded umbo situated just anterior to 

 mid-length and strongly incurved to the prosogyrous beak. Anterior margin 

 strongly convex, curved in continuity with ventral margin, the anterior part of which 

 has a shallow sinus in some specimens. Posterior wing of feeble convexity, rounded 

 at its tip, which is level with or extends to a variable extent beyond the posterior 

 extremity of the ventral margin ; wing separated from inflated body of valve by 

 radial sulcus to which there corresponds a sinus of posterior margin. Ornament 

 consisting of regularly arranged concentric ribs absent from posterior wing in some 

 specimens. 



Holotype and paratypes. Holotype, no. LL. 13246. About 15 paratypes. 



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

 Callovian], Asaharbito Beds. 



Remarks. In this species the ventral margin extends further in a posterior 

 direction than in the European Kimmeridgian species Cuspidaria fontannesii (de 



