294 Ajinals of the So7ith African Museu77t. 



posteriorly. Posterior margin rather short, slightly oblique. Postero- 

 dorsal margin long, slightly concave. Umbones inconspicuous, 

 recurved, situated at a distance from the anterior end equal to a 

 third or more of the total length of the valve. Area rather broad, 

 flattened, with a gentle dorsal slope, and divided near its middle by 

 a shallov^ furrow. Near the umbo there is a narrow carina, but 

 posteriorly it is absent or indistinct. Escutcheon rather small, 

 sloping gradually in the neighbourhood of the umbo, but more 

 rapidly behind. 



Sides of valves ornamented with from 17 to 20 narrow, tuberculate 

 costae separated by broad, shallow interspaces. Near the umbo the 

 costae form a large curve and are very oblique to the margin of the 

 area, but in passing posteriorly the curvature decreases and they 

 become less oblique to the area. Near the umbo the costae are 

 continued on to the area, but the larger part of the area is almost 

 smooth except for fine growth-ridges. On the escutcheon there are 

 narrow costellae with broad interspaces. In young specimens 

 numerous fine, concentric, linear ridges run obliquely across the 

 costae and interspaces. 



Length 32 . 27 . 20 mm. 



Height 28 . 23 . 17 „ 



Affinities. — T. elegans does not appear to be closely allied to any 

 other species. It shows a slight resemblance to T. Meyeri, Lycett,"^- 

 but differs from it in several respects. 



Bemark. — The type is in the Museum of the Geological Society of 

 London. 



Family MYTILID^. 



Genus MYTILUS, Linnaeus. 

 Plate XXXV., fig. 5. 

 A single imperfect specimen of a left valve of Mytilus or some 

 closely allied form is in the Griesbach collection belonging to the 

 Hamburg Museum. 



Genus MODIOLA, Lamarck. 



MODIOLA KAFPEARIA, Sp. nOV. 



Plate XXXV., fig. 6. 

 Description. — Shell ovate-oblong, very convex, with rounded 

 extremities. Ventral margin nearly straight ; the opposite margin 

 * Brit. Foss. Trigoniae (1875), p. 125, pi. xxiii., fig. 6, pi. xli., figs. 15, 16. 



