IN THE ESNA-IDFU REGION, NILE VALLEY, EGYPT 77 



ed marginal keels ; curved, raised, beaded dorsal sutures and radial incised ventral 

 ones ; thick limbate umbilical flange ; very wide umbilicus, and generally rough 

 surface. 



Description. Test large, quadrilobate in outline, planoconvex, umbilicoconvex, 

 coiled in a very low trochospire ; dorsal side almost flat although the early chambers 

 are very weakly raised above the circumambient last whorl ; ventral side strongly 

 inflated and distinctly protruding ; equatorial periphery roughly quadrate, very 

 distinctly lobate, with two well-developed, much thickened, beaded keels ; axial 

 periphery truncate ; chambers on the dorsal side 17, arranged in 3 dextrally coiled 

 whorls ; the initial ones are small, inflated, globigerine, increase slowly in size and are 

 followed by typically crescentic chambers which increase moderately in size as 

 added ; the last whorl is composed of 4, large, petaloid chambers which increase so 

 slowly that they all appear to be equal in size ; on the ventral side the chambers are 4, 

 large, roughly ovoid, distinctly protruding and increase very slowly in size ; sutures 

 on the dorsal side are curved, raised, thickened and beaded ; on the ventral side they 

 are short, radial and depressed ; umbilicus quadrate in outline, very wide, deep, 

 surrounded by much thickened, limbate, delicately beaded ridges, and covered by 

 complex tegilla of which remnants are still preserved ; primary apertures interio- 

 marginal, umbilical ; tegilla with accessory apertures only poorly preserved ; 

 wall calcareous, perforate except for the imperforate keels, peripheral band and 

 tegilla ; surface distinctly papillose in the early part, smooth in the later part with 

 the papillae extremely well developed on the early chambers of the last whorl 

 especially on the ventral side ; the two marginal keels are almost parallel to each 

 other and enclose a wide, depressed peripheral band. 



Dimensions of described specimen. 

 Maximum diameter = 0-48 mm. 

 Minimum diameter = 0.43 mm. 



Thickness = 0-23 mm. 



Main Variation. 



1. Chambers 15-19, arranged in 2^-3 whorls ; generally dextrally coiled but 



sinistral forms also occurr (out of 500 specimens picked at random, 4 coiled 

 sinistrally) . 



2. Chambers in the last whorl 4-4I, very rarely 5, increasing very slowly in size. 



3. Chambers on the dorsal side flat, very weakly inflated, sometimes even 



depressed ; on the ventral side the chambers are always strongly inflated. 



4. Marginal keels, sutures and umbilical flange either heavily papillose or just 



thickened and limbate. 



5. The two keels are either equally developed or the ventral keel is sometimes 



reduced on the last chamber. 



6. Surface delicately papillose in early part, smooth in later part ; sometimes 



the papillae are so strongly developed that they give the surface a roughly 

 nodose, or even spinose appearance. The beads on the marginal keel also 

 taper out sometimes in the form of spine-like projections. 



