570 MR R. BULLEN NEWTON ON SOME CRETACEOUS BRACHIOPODA 



obscure, through possible erosion, for a more complete description of an otherwise 

 interesting specimen. 



Occurrence. — A limestone specimen and more or less of a cast ; the surface is 

 tinged with a brownish colour. It was found associated with Trigonarca, crinoidal 

 stem ossicles, etc. 



Locality. — No. 292 — Canyon E. of Old Lobito. 



Fam. ArcidvE. 

 Trigonarca cf. ligeriensis, Orbigny. (PI. I, figs. 12 and 13.) 



Area ligeriensis, Orbigny: Pal. Frangaise: Terr. Cretaces Lamellibranchia, 1844, vol. iii, pi. 317, 



figs. 1-3, p. 227 {rum figs. 4 and 5). 

 Trigonarca ligeriensis, R. B. Newton: Trans. Roy. Soc. Soutli Africa, 1909, vol. i, pi. iv, figs. 13-18, p. 33. 



Remarks. — A small form of Trigonarca occurs rather plentifully in the cream- 

 coloured limestones, mostly as natural casts. The specimens are rather more 

 quadrate than in the normal condition of this species ; otherwise they are closely 

 related, and may even be young examples. One specimen fits into a limestone 

 impression which exhibits the strongly and divergently grooved ligament region — 

 the teeth on the cast itself possessing striations on the lateral surfaces. The same 

 impression shows remains of external sculpture which consists of fine and closely 

 arranged concentric striations crossed by obscure radial lines, which is especially 

 well seen around the umbonal region. 



Distribution. — The species is known from the Cenomanian of Europe, Syria, 

 Egypt, and Zululand. 



Occurrence. — These casts are found in the cream-coloured limestone associated 

 with Trachycardium, etc. 



Localities.— N os. 281, 292— Plateau N. of Lobito (28 1) ; Canyon E. of Old 

 Lobito (292). 



Trigonarca cf. diceras, Seguenza. 



Area diceras, Seguenza : Studi geol. Cretaceo Italia : Atti Accad. Lined {Roma), 1882, ser. 3 ; Mem., vol. xii, 



pi. xiv, fig. 1, p. 158. 

 Area (Trigonoarca 1) diceras, Pervinquiere : JStudes Pal. Tunisienne : Gast. Lamell. Cretaces, 1912, pi. vii, 



figs. 23, 25, 26, p. 102. 



Remarks. — This determination refers to a rough limestone cast exhibiting both 

 valves in the closed condition, and showing a pair of very anterior, distant umbones 

 that are separated by a wide and deeply excavated cardinal region, while the 

 adductor scar impressions are represented by large and prominent pits of more 

 or less trigonal contour. 

 Dimensions.- — 



Length ...... 68 mm. 



Height . . . . . 42 „ 



Diameter . . . . 50 „ 



