R. Bidlen Newton — Egyptian Lower Tertianj Shells. 537 



costal grooves. The absence of spines, also, separates the new- 

 form from S. multistriatus of Deshayes, and from Schafhautl's ' 

 Kressenberg species, S. astragalus. 



This species is represented by six specimens, the largest (a lower 

 valve) measuring 44 X 41 millimetres, the remainder being of more 

 uniform size and having united valves. They are in a fair state of 

 preservation, without sinnous attachments to the ribs, nor is there 

 any indication of striations between the grooves. The matrix is 

 a white chalky foraminiferal (OperciiHna, etc.) limestone and similar 

 to that containing Chania late-costata. 



Horizon. — Lower Eocene (Libyan Series). 



Distribution. — Egypt : near Assiout." Coll. Geol. Surv. Egypt 

 (No. 630, Box No. 33a). 



Genus CHAMA, Linnaeus. 

 Systema Naturas, 1758, ed. x, p. 691. 

 Type. — C. lazarus, Linnaeus. 



Chama late-costata, Bellaidi. (PL XX, Figs. 1-3.) 

 CJiama late-costata and C. latilamellata, Bellardi, " Cat. Kais. Foss. 

 Nummulitiques Nice " : Mem. Soc. Geol. France, ser. ii, 

 vol. iv (1851), p. 254, pi. xx, fig. 12. 

 Description. — Testa ovato-rotundata, subeqtiivalvis, Icevi, con- 

 centrice costata ; costis lamellosis, postice subimbricatis, distantibus 

 dente cardinali recurve, crasso, Icevi ; iimbonibus recurvis, subspiratis 

 (Bellardi). This is the original diagnosis of a shell which 

 is mainly distinguished from other Chamce by the widely distant 

 concentric ribs ornamenting its valves. The upper valve is more 

 sculptured than the other, possessing numerous pillar-like, radial 

 costae in the concentric spaces, thereby connecting the species 

 very closely with C. calcarata, Lamarck, from the Paris Basin 

 Eocenes. Although somewhat worn, the Egyptian specimens 

 show all these details of structure, besides preserving some faint 

 indications of concentric striee between the primary costse of the 

 lower valve. No interiors are seen. 



Dimensions. 



Largest lower valve — Height ... ... 42 mm. 



Length ... ... 37 ,, 



Diameter 15 ,, (about). 



Eemabks. — Found in a white chalky foraminiferal limestone 

 stained with iron peroxide, and accompanied by a Spondylus. The 

 smallest and most perfect specimen has both its valves united. 



Horizon. — Lower Eocene (Libyan Series). 



Distribution. — Environs of Nice (Bellardi); Pyrenees (D'Archiac); 

 Spain (Mallada) ; Egypt, near Assiout. Coll. Geol. Surv. Egypt 

 (No. 636, Box No. 47a). 



^ Siid-Bayerns Lethasa Geoguostica der Kressenberg, etc., 1863, p. 148, pi. 65b, 

 fig. 13. 



