FROM TANGANYIKA AND KENYA 29 



Genus ROLLIERIA Cossmann 1920 



Rollieria aequilatera (Koch & Dunker) 

 PI. i, figs. 5«, b, c 



1837. Tellina aequilatera Koch & Dunker : 30, pi. 2, fig. 9. 

 1850a. Leda delila d'Orbigny : 253. 



1869. Leda aequilatera (Dunker & Koch) ; Brauns : 267. 

 1908a. Leda delila d'Orbigny ; Thevenin : 57, pi. 14, figs. 28-30. 



Material. One specimen (no. LL. 35005). 



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

 Upper Lias, Toarcian, Didimtu Beds. 



Remarks. Rollieria includes the small, ovate, equilateral, compressed nuculanids 

 which range throughout the Jurassic and are difficult to separate into species. 

 Elsewhere (Cox 1936 : 464) I have applied the name Nuculana {Rollieria) bronni 

 (Andler) to a species ranging from Lower to Middle Lias. I refer the present Upper 

 Liassic specimen to R. aequilatera (Koch & Dunker), a species based on an Inferior 

 Oolite specimen, and I place Leda delila d'Orbigny, based on a Toarcian specimen, 

 in synonymy, as was suggested by Brauns (1869). The range of R. aequilatera 

 extends, according to that author, to the ornatus-beds (Callovian). The specimen 

 from the Yorkshire Upper Lias figured as Leda aequilatera by Tate (1876, pi. 11, 

 fig. 10) was wrongly identified and not even a Rollieria. The present specimen from 

 Kenya, which is 9 mm. long, has the outline of a typical Rollieria, and is referred to 

 the genus with confidence although it shows no hinge-teeth. 



Superfamily ARCACEA 



Family PARALLELODONTIDAE Dall 1898 



Genus PARALLELODON Meek & Worthen 1866 



Parallelodon pindiroensis sp. nov. 



PI. 1, figs, ya, b, 8a, b 



Diagnosis. Of medium size (length of holotype c. 33 mm.), subrectangular to 

 trapeziform in shape, variable also in ratio of length to height. Umbones rising very 

 little above hinge-margin, broadly rounded or with a slight median depression ; 

 beaks at anterior third or quarter of length of shell. Hinge-margin extended 

 posteriorly as a short, acutely pointed wing, the tip of which lies almost exactly 

 above posterior end of body of shell. Posterior area much compressed, not sepa- 

 rated from the flank by a distinct carina, but bordered near the umbo by a broadly 

 rounded ridge which soon dies out. A median depression of the flank and a corres- 

 ponding broad sinus of the ventral margin are variably developed. Cardinal area 

 rather narrow. Posterior area bearing very weak radial riblets, the remainder of the 

 surface radial threads which are obscure except on the antero-dorsal region ; growth- 

 rugae present at irregular intervals. 



