New Fossils from the Bokkeveld Beds. 393 



NUCULANA VIATOR sp. nov. 

 (PI. XLVII., figs. 11, 11a.) 



There is one internal cast of a species of Nuculaua which is 

 undoubtedly distinct from N. inornata, and probably belongs to 

 a new species. It most resembles in shape the form termed by 

 Ulrich * Leda sp. a, from the Devonian of Bolivia, which (as Ulrich 

 has remarked) differs from N. inomata by having the beaks more 

 centrally situated and the posterior end less produced. In our 

 shell the dorsal margin behind the beaks is also rather more exca- 

 vated, the ventral margin more convex and the posterior extremity 

 more acutely pointed. The whole shell is shorter and cannot be 

 regarded as a variety of N. inornata. The hinge-line is fairly well 

 preserved, is only weakly angulated, and shows about 10 teeth 

 in front of the beaks extending about half-way to the anterior 

 end of shell. Behind the beaks the teeth are smaller and less 

 distinctly shown, and there is a narrow oval scar on each side of 

 and close to the hinge-line at about a third of its length from 

 the beaks. The anterior and posterior adductor scars are faintly 

 marked. 



Dimensions. — Length 17 mm. ; height 11 mm. ; thickness 6 mm. 



In addition to Ulrich's Leda sp. a its nearest allies seem to be 

 Leda brevirostris Hall, t of the Hamilton Group, and N. Ahrendi A. 

 RcEm.j of the Upper Coblenzian. 



This new Bokkeveld form deserves a name, and may be termed 

 N. viator. It comes from the Zwartberg Pass. 



NUCULANA AGRESTIS sp. nov. 



(PI. XLVIL, tigs. 12, 12a.) 



Shell short, subtriangular, compressed, flattened, most convex 

 below beaks, narrowing rapidly posteriorly. Anterior end high, 

 obtuse, broadly rounded. Beaks small, acute, rising above hinge- 

 line, situated a little behind anterior third of shell, slightly directed 

 backwards. Dorsal margin nearly straight, sloping downwards 

 rapidly to subacute narrow posterior end which is not produced. 

 Ventral margin strongly convex. Hinge-line angulated below beaks 



* Ulrich, op. cit., p. 45, t. ii., fig. 14. 

 t Hall, op. cit., pi. xlvii., figs. 38, 39. 

 t Beushausen, op. cit., p. 04, t. iv., figs. 37-39. 



