102 Annals of the South African Museum. 



1882. Trigonia herzogi G. Steinmann, Neues Jahrbuch fur Mine- 

 ralogie, Band i., p. 220, Taf. vii., figs. 1, 2 ; Taf. ix., 

 figs. 1, 2. 



Occurrence. This is an abundant and characteristic form in the 

 Sunday's Eiver Beds. It was recorded by Hausrnami from the 

 neighbourhood of Enon, and by Krauss from the left bank of the 

 Zwartkop's River below Uitenhage ; also by Stow :;: from various 

 localities on the Sunday's and Zwartkop's Elvers. A fine specimen 

 sent to me from the South African Museum is from the Sunday's 

 Eiver (289). Messrs. Rogers and Schwarz found T. licrzogi on the 

 north side of the Zwartkop's River at a locality to the west of 

 Rawson Bridge, and at Picnic Bush; also further up the river on the 

 road from Perseverance Farm to the Salt Pan, and at Cuyler Manor. 

 Near Uitenhage, they record this form from two beds of sandstone 

 exposed in dry watercourses on the ascent of the Grass Ridge road ; 

 in the railway cutting between milestones 24-| 24f on the Graaff- 

 Eeinet railway; and on the road to Hillwacht, where the path leaves 

 the plain. On the Sunday's River it was found near the top of the 

 white krantz on Wolve Kraal, on the north bank of the river. 



The collection made in 1905 by Mr. Rogers includes several 

 specimens of T. herzogi, which came from the following localities: the 

 left side of Coega Valley, two miles down from the railway (468g) ; 

 from the valley east of the railway, one mile up the line from 

 Coega station (474g) ; the cliff on Buck Kraal, Sunday's River 

 (116h, 120h, 122h) ; and the cliffs on Zoet Geneugd, Sunday's 

 River (99h). 



Bemarks. Trigonia heriogi is well known from the striking figme 

 given by Goldfuss, illustrating a fine specimen which was included 

 in a small collection of Uitenhage molluscs obtained by Hertzog. 

 These had been previously noticed briefly by Hausmann in his 

 paper on the geology of South Africa.! The shell is conspicuous 

 for its large size and elongated outline, its straight and lengthened 

 cardinal margin and its straight, nodose ribs, backwardly inclined 

 in the posterior half of a fully grown valve. It was referred by 

 Pictet and by Lycett to the section Quadrate. An excellent figure 

 of the shell was given also by Steinmann, who included T. herzogi 

 with T. transitoria Steinm. in the group Pseudo-quadrat, the 

 characters of which are briefly discussed below in the remarks 

 appended to the description of Trigonia holiihi. Steinmann has set 

 forth in great detail the differences that distinguish T. herzogi from 



* Stow (1), pp. 498-505. f Hausmann (1), p. 1458. 



