The Invertebrate Fauna of the Uitenhage Series. 91 



(Wealden) * is rather less equilateral, the umbonal region is more 

 prominent, and the antero-superior border more steeply sloping. 



Unio martini J. de C. Sow. (Wealden) f is more equilateral, much 

 higher and less slender in figure, and probably a more inflated 

 form. 



Unio subsinuata Koch and Dunker, J from the Wealden of North 

 Germany, is in some respects similar, notably in the form of the 

 posterior half of the shell and the position of the umbones, but 

 differs markedly in the horizontally produced superior margin in 

 front of the umbones. Unio voltzi Koch and Dunker, though 

 regarded by those authors as distinct from the last, differs in similar 

 manner from Unio uitenhagensis. Unio planus Eoem.|| is more 

 compressed in form and has a less sloping antero-superior outline. 



A comparison with the figures and descriptions of the forms of 

 Unio from the Jurassic and Cretaceous rocks of North America 

 does not show that resemblances exist which call for special remark. 



GENUS TEIGONIA J. G. Bruguiere. 



TRIGONIA VENTRICOSA (Krauss). 

 Plate III., figs. 1, la. 



1843. Lyriodon ventricosa F. Krauss, Amtlicher Bericht iiber die 

 zwanzigste Versammlung der Gesellsch. deutsch. Natur- 

 forscher und Aerzte zu Mainz im Sept., 1842, p. 130. 



1850. Lyrodon ventricosus F. Krauss (partim), Nov. Act. Acad. 

 Caes. Leop. -Carol. Nat. Cur., vol. xxii., pt. 2, p. 456, 

 Tab. 49, figs. 2c-2/, (exclude figs. 2a, 26). 



1871. Trigonia ventricosa F. Stoliczka, Cretaceous Fauna of 

 Southern India, vol. iii., The Pelecypoda; p. 315, 

 pi. xv., figs. 9. 9a. (Palaeontologia Indica.) 



1875. Trigonia ventricosa J. Lycett, Mon. Brit. Foss. Trigoniae, 

 p. 119, and text-figures. (Palaeontographical Society.) 



1877. Trigonia ventricosa O. Feistmantel, Foss. Flora of the 

 Gondwana System, vol. i., pt. 3, p. 164. (Palaeontologia 

 Indica.) 



* J. de C. Sowerby (1), vol. vi., Tab. 594, figs. 3-5 (1828). 



t J. de C. Sowerby (2), p. 346, pi. xxi., fig. 17. 



J Koch and Dunker (1), p. 58, Tab. vii., fig. 2 ; Dunker and Meyer (1), p. 26, 

 Taf. xi., figs. 4, 5. 



Koch and Dunker (1), p. 59, Tab. vii., fig. 3. 



|| F. A. Roemer (1), p. 95, Taf. v., fig. 14 ; Dunker and Meyer 1), p. 27, Taf. xi., 

 fig. 8. 



