398 Annals of the South African Mmenm. 



Genus NYASSA Hall, 1869. 



NYASSA AEGUTA Hall. 



A specimen which the author" referred doubtfully to Hall's 

 Nyassa arguta has been described on a previous occasion from the 

 Zwartberg Pass. Three, or possibly four, more examples of the 

 same species from the same locality are now to hand, and there can 

 be no doubt as to their reference to N. arguta. The elongated post- 

 lateral parallel teeth or cardinal ridges and the small irregular trans- 

 verse pits on the plate below the beak can be detected, and if Beus- 

 hausen is correct in identifying N. dorsata Goldf. with N. arguta Hall, 

 we can have no hesitation in referring this South African form to it. 

 Clarke's f Guerangeria or Nyassa ortoni from the Devonian of 

 Brazil is closely allied. 



Genus MODIOMORPHA Hall, 1873. 



MODIOMORPHA BAINI (Sharpe) var. 



There are two specimens from Klein Straat Siding, both of left 

 valves, of a species of Modiomorpha which may be regarded as a 

 variety of Sharpe's Modiolopsis haini, of which examples have been 

 previously described by the author \ from this and other localities. 

 A somewhat distorted specimen of a right valve from Koudeveld Berg 

 may be referred to the same variety. The distinguishing feature is 

 the more elongate sublinguiform shape of the shell, therein resem- 

 bling Clarke's M. hehnreicheni § more than M. Baini. They are 

 also flatter and have the umbonal ridge less strongly developed than 

 in the latter, but this may be due to lateral compression. The beaks 

 are more anterior in M. Baini and this variety than in M. hehn- 

 reicheni, and differ from Cypricardella pohli Clarke (with which 

 some Cape specimens have been identified) by the axis of the 

 shell not being oblique and in other respects. There can be little 

 doubt that they belong to the genus Modiomorpha, the muscle-scars, 

 position of beaks, hinge-line, and general shape being essentially in 

 agreement with typical members. The length of one of our speci- 



* Reed, Geol. Mag., Dec. 5, vol. iii., 1906, p. 303, pi. xvi., figs. 3, 3a. 



t Clarke, op. cit., p. 62, pi. vii., fig. 6. 



+ Eeed, Ann. S. Afr. Mus., vol. iv., pt. vi., 1904, p. 267. 



§ Clarke, oj). cit., p. 50, pi. vi., figs. 1, 2, 17. 



