Mollusca from the Bokkcvehl Beds. 253 



end rather produced and obliquelj^ truncated above but rounded 

 below ; the cardinal line is straight. The surface of the valve is 

 moderately convex ; there is no distinct umbonal ridge, but a very 

 faint shallow depression runs down from the beak to the anterior 

 third of the basal margin, and there is a trace of a very weak 

 oblique impressed line behind it. The ornamentation consists of 

 concentric stritc and weak wrinkles of unequal size. 



Diviensions. — Length (about) 32 mm. ; height (about) 17 mm. 



Affinities. — The state of preservation of this shell is too poor to 

 make a useful comparison with other species ; but it certainly 

 belongs to a species distinct from any hitherto recorded from the 

 Bokkeveld Beds. 



Locality. — (No. 98) Ceres. 



GEAMMYSIA COREUGATA (Sharpe). 



1856. Sangjditolites ? corrugatiis, Sharpe, Trans. Geol. Soc, ser. 2, 

 vol. vii., p. 212, pi. xxvii. fig. 8. 



This species was described by Sharpe as follows : " Shell trans- 

 versely rhomboidal w^ith a depression down the middle of each valve, 

 bounded by a broad obtuse keel [umbonal ridge] which reaches 

 from the umljo to the posterior ventral margin ; beaks prominent 

 and close to the rounded anterior end ; valves covered with coarse 

 concentric wrinkles and finer lines of growth. Length [height] 

 ^ inch; breadth [length] 1 inch; thickness ^ inch." 



The material on which this species was founded consists only of 

 two external casts of the valves of one individual. From an 

 examination of these types it may be added to the above description 

 that the valves are decidedly gibbous and tumid ; the umbonal ridge 

 is broad, rounded, and slightly curved ; the depression which Sharpe 

 mentions is rather a flattening of the surface ; and there is a sharply 

 impressed area below the beaks. Ulrich ■'■ mentioned a shell in the 

 Bolivian Devonian which he considered belonged probably to Moclio- 

 lojjsis and allied to this species ; but there does not seem to be any 

 reason for referring the South African form to this genus, and it 

 appears to be more allied to the small Brazilian species Grammi/sia 

 ulrichi, Clarke. t 



Locality. — Leo Hoek. | 



* Ulrich, op. cit., p. 49. 



t Clarke, op. cit., p. 67, pi. vii., fig. 12. 



t Now known as Leeuwen Fonteiii, ^Varm Bokkeveld. 



