The Invertebrate Fauna of the Uitenhage Series. 139 



shaped, flattened form, and though their depth cannot be satisfac- 

 torily measured in either specimen, it could not have exceeded two 

 or three millimetres. In the example from Olifant's Kop, the pallial 

 border does not lie in a median plane of symmetry, but is laterally 

 bowed, with a slight convexity towards the observer. This may 

 possibly have been an individual abnormally distorted in life, or the 

 distortion may perhaps have been brought about during the process 

 of fossilisation, but it was probably not a normal character. 



Anthonya cultriformis Gabb,* the type-species of the genus, from 

 the Cretaceous rocks of California, differs in being considerably 

 more elongated and attenuated posteriorly, and in having more 

 oblique posterior truncation. It also lacks the close linear orna- 

 ments which cover the whole surface of A. lineata, though it has a 

 similar type of sculpture in the umbonal region. 



A. cantiana Woods,! from the Folkestone Beds of Folkestone, is 

 more inequilateral, with the umbonal region more elevated and 

 nearer to the anterior extremity. A species described by Mr. Woods, 

 though unnamed, from the Lower Greensand of Atherfield, is 

 distinguished by the posterior elongation and attenuation of its 

 shell, and by its smooth surface. 



Anthonya cornueliana (d'Orb.) J appears to approach more closely 

 in form, especially such a specimen as that figured by Miss Skeat ; 

 but A. lineata is less inequilateral and is not so obliquely truncated 

 posteriorly. 



GENUS TANCKEDIA J. Lycett. 

 TANCREDIA SCHWARZI sp. nov. 



Plate VII., figs. 9, 9a, 10. 



Description. The shell has an elongated trigonal outline, well 

 produced anteriorly. The umbonal region is prominent, the margin 

 before and behind it falling away rapidly. The umbo is situated 

 within the posterior half of the valve, though not distant from the 

 middle ; it is fairly strongly incurved. The upper margin in front of 

 the umbo forms a straight line in profile, and only curves on reaching 

 the anterior extremity, where it passes by a sudden and sharp bend 

 into the long, gently convex inferior margin. At the posterior 

 end of the short, straight hinge-line the shell-outline is obliquely 



* Gabb (1), p. 182, pi. xxx., fig. 236. 



f Woods (3), vol. ii., part 3, p. 130, pi. xix., figs. 4, 5 (1906). 

 J d'Orbigny (3), p. 74, pi. cclxiv., figs. 7-9 (1844), described as Crassatella ; 

 Skeat and Madsen (1), p. 178, pi. vi., fig. 13 (as Ptychomya). 



