AND MOLLUSCA FROM ANGOLA, PORTUGUESE WEST AFRICA. 579 



The specific name is in honour of Prof. J. W. Gregory, F.R.S., who, from a 

 series of extended studies as well as from personal surveys, has greatly advanced our 

 knowledge of African geology. 



Occurrence. — The cast is in a cream-coloured limestone, and was found associated 

 with an Ammonite of the Schloenbachia injiata type. 



Locality. — No. 266 — plateau south-west of Hanha. 



EXPLANATION OF PLATES. 

 (Figures are of the natural size, except when otherwise specified.) 



Plate I. 

 Terebratula depressa, Lamarck. 



Fig. 1. An external view of the ventral or pedicle valve, the ohlique lateral margins and concentric 

 growth striations being well marked. 



Locality. — Hanha, near Lohito (No. 12). 



Neitliea sequicostata (Lamarck). 



Fig. 2. External aspect of a small lower valve with a similar length and height, exhibiting a series 

 of equal costse. 



Fig. 3. Magnified view of costre of same specimen, showing an obscure transversely striated sculpture. 

 Locality.— E. of Lobito (No. 294). 



Neitliea angoliensis, sp. nov. 



Fig. 4. Lateral view of lower valve, showing the six robust primary costse with a secondary rib between 

 each, of apparently shorter length, x 2. 



Locality. — 80 metres above the Catumbella Dam (No. 20). 



Neithea tricostata (Coquand). 



Fig. 5. Lateral view of a large lower valve, showing the six primary costaj with the interspaces 

 occupied by the three unequal and nearly equidistant ribs. 



Fig. 6. Anterior aspect of same specimen, exhibiting the curvature and structure of the costal system. 

 Fig. 7. Magnified details of sculpture, showing the close and undulating concentric striations. 

 Locality. — Lobito ; collected by Mr E. Robins. 



Neithea quadricostata (J. Sowerby). 



Fig. 8. An internal view of a small upper valve embedded in limestone, showing a large posterior ear, 

 the flattened-looking ribs indicating a series of broad furrows. 

 Locality. — Catumbella Dam (No. 19). 



Lima cf. itieriana, Pictet and Roux. 



Fig. 9. Right lateral aspect of a limestone cast, showing about twenty ribs with resemblances to 

 this species. 



Locality. — E. of Lobito (No. 294). 



Volsella sp. 



Fig. 10. Dorsal view of specimen with united valves, showing considerable tumidity. 

 Fig. 11. Left lateral aspect of same specimen concentrically striated. 

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



