FROM WEST PAKISTAN 



65 



Element 

 Anterior 



Anteromedian 

 Posteromedian 



Posterior 



Dimensions (mm). 



Left valve 



Deep rounded socket. 



Conical projecting tooth. 

 Denticulate bar. 



Elongate groove, 

 presumably deep (filled 

 in with matrix). 



Right valve 



Projecting conical tooth. 



Eye-socket opens below 



and slightly anterior to 



this tooth. 



Socket opening into groove. 



Shallow locellate groove 



narrowing towards posterior. 



Subpessular tooth, higher 



on the posterior side. 



L 



o-55 

 0-56 



H 



0-32 



o-34 



W 

 0-30 



o-34 



Io. 4230 Carapace male 



Io. 4231 Carapace female 



Io. 4232 Right valve female (broken) — Jw, 0*17 



Comparison. Phalcocythere spinosa sp. nov. closely approaches the present form 

 but is smaller, has a less reticulate and spinose surface and a more concave postero- 

 dorsal slope. Phalcocythere retispinata sp. nov. is much larger, has a slightly convex 

 dorsal margin particularly in the female dimorph, and the carapace tapers towards 

 the posterior. 



Remarks. The specimens studied were made available through the kindness of 

 Dr. F. E. Eames, lately Chief Palaeontologist of the British Petroleum Co. Ltd. 

 These specimens may represent a distinct sub-species of P. spinosa. 



Genus QUADRACYTHERE Hornibrook 1952 

 Type species. Cythere truncula Brady 1898. 



Subgenus HORNIBROOKELLA Moos 1965 

 Type species. Cythere anna Lienenklaus 1894. 



Quadracythere (Hornibrookella) platybomus sp. nov. 

 (Plate 33, figs. 14, 15, 18, 19). 



Derivation of name. Greek platys, broad -f- bomos, bottom ; with reference to 

 the expanded venter. 



Diagnosis. Carapace with expanded venter, subrectangular to subquadrate in 

 lateral outline. 



Holotype. Io. 4351, a male carapace (PI. 33, figs. 14, 18). 



Paratype. Io. 4300. 



Material. Nine specimens from the locality below from two horizons (sample 

 nos. 460-i and 460-0) . GSP BM 2581-2. 



