I 



i 



296 E. 2f. Brydom — Further Notes on the Trimmingham Chalk. 



middle at a point on a line with tlie upper edge of tlie aperture, 

 which is small and transversely oval, with a strongly denticulated 

 lower lip. 



EscHAUA KowEi, sp. nov. (Fig. 6.) 



Colony free, bilamellate, growing in expanding fronds, which are 

 very fragile. Cell long and narrow, aperture occupying quite half 

 the cell, heel-shaped, and elongated, with sides constricted close to 

 the lower lip, and a strongly projecting lower lip. No ovicell. 

 Avicularium an elongated cell with pointed ends, broad in the middle. 



Fig. 6. 



tapering more rapidly below than above. Aperture rather below the 

 middle, appearing under a low power as a transverse oblong with 

 rounded corners, and a distinct pore above and a faint pore below (a). 

 Under higher powers the structure shown in (6) is revealed. This 

 structure is rarely preserved, the specimens generally presenting 

 it in varying degrees of ruin. 



Cribeilina Sherborni, sp. nov. (Fig. 7.) 



Colony always adherent. Cell widely oval, apparently based on 

 a primitive form (a), with an elongated heel-shaped aperture in 

 a plane at a slight angle to the horizontal, a front wall rising from 

 all sides to a central circular phitforra in which are cut a Sf ries of 

 radiating furrows, two long lateral slits in the front wall commencing 

 between the aperture and the margin and running outwards close to 

 the margin, and a globose ovicell at the top of the cell some distance 

 above the aperture. The first stage of development appears to be 

 that the lower lip of the aperture rises slightly, and the rest of the 



Fig. 7. 



margin of the aperture rises considerably to form with the upper 

 edge of the aperture of the ovicell an oval secondary aperture (6). 

 Next there are developed over the lateral slits lateral avioularia, set 

 on legs so as to allow free access of water to the slits (r). These 

 avicularia are very faintly mandibular, with the point of the mandible 

 on the inner side, but the least attrition makes them circular. At 

 the same time the sides and base of the secondary aperture are 

 further raised, and the sides are produced up the sloping surface of 

 the ovicell to meet at the central crown. In the final stage (d) the 



