The Invertebrate Fauna of the Uitenhage Series. 87 



make it clear that the vertical striping on the lower part of the flank 

 is developed in that form also ; the same occurs in M. medus 

 (d'Orbigny), an allied shell from the Kimeridge. 



A shell of very similar type to M. baini is M.flagellifera (Forbes)," 

 from the Upper Cretaceous of Europe and Southern India ; but an 

 examination of the type specimens in the Geological Society's collec- 

 tion shows that these have the ribs dividing chiefly into groups of 

 three, and the lower part of the flank entirely lacks any traces of the 

 fine vertical stripes. 



A fragment of a similarly ornamented, elongated Modiola from the 

 Cenomanian of the Sarthe, was considered by d'Orbigny to be speci- 

 fically distinct from others previously described, and was figured by 

 Guer anger f as Mytilus sarthensis. It may be clearly seen from 

 that author's photographic illustration that this differs from M. baini 

 by the relatively greater disparity in the number of large and small 

 ribs ; in the French shell there are three small ribs to each of the 

 major ribs. 



Modiola rubidgei (Tate),| from the Uitenhage Marine Beds, also 

 bears a general resemblance to M. baini. In M. rubidgei, however, 

 the ornaments on the upper part of the valve consist of relatively 

 few, gently rounded folds in place of the well-defined narrow rounded 

 ribs in M. baini; in addition, these folds are themselves ornamented 

 by finer linear markings which pass backwards along them and then 

 curve forward to run parallel to the lower margin. In M. rubidgei 

 there is also an absence of vertical striping on the lower part of the 

 valve. 



GENUS NUCULA Lamarck. 



NUCULA UITENHAGENSIS Sp. nOV. 



Plate II., fig. 13. 



Description of a Single Specimen. The shell is oval in outline, 

 short and high posteriorly, moderately inflated. The cardinal 

 margin slopes down forwards from the umbo with a gently convex 

 outline, and passes by a curve into the rather short anterior margin. 

 The posterior margin falls steeply from the umbo and passes by a 

 rather sharp curve into the long, gently convex inferior margin. 

 The greatest height is at the umbo. The umbonal region is rounded 

 and broad, and not strongly prominent. From the umbo a very 

 faintly developed, blunt ridge of the valve-surface passes forward, 



* Forbes (2), p. 152, pi. xvi., fig. 9 ; Woods (3), vol. i., p. 99, pi. xvii., figs. 1, 2 

 (1900). 



f Gue"ranger (1), p. 17, pi. xxiii., fig. 1. { Tate (1), p. 157, pi. ix., fig. 11. 



