6o R. BULLEN NEWTON on 



right posterior corner, whereas the septum in true forms of Calyptraea is 

 more an attachment of the periphery and consequently occupying a fairly 

 shallow area of the aperture. Again, the present shell shows a sub-marginal 

 spiral region which in Calyptraea is more central. Its ornamentation, 

 consisting of distant spiral rows of perforated tubercles and numerous oblique 

 striations, resembles very much the sculpture of Solander's Trochus apertus 

 from the Barton beds of Hampshire, a form, however, which is regarded as 

 a separate species chiefly on account of the more central spire and the 

 septum's attachment to the periphery. Only two examples of this shell were 

 found in the Nigerian deposits, the larger one measuring 13x11 mm. possessing 

 good spiral and sculpture characters, while the smaller illustrates the position 

 of the internal diaphragm and umbilicus. The species appears to be restricted 

 to the Lutetian portion of the Eocene series. 



DISTRIBUTION. Lutetian of Europe. 

 OCCURRENCE. Cutting (No. not stated). 

 COLLECTOR. Mr. Kitson. 



Pelecypoda. 



Family 

 Oatrea of. marginidentata, S. V. Wood. 



PLATE 6, Figs. 2-5. 

 Ostrea marginidentata. 



S. V. Wood: Eocene Mollusca, England, Mon. Pal. Soc., 1861, pi. 5, fig. 2, p. 27. 



REMARKS. The largest of the specimens represented under this category, 

 consists of an imperfect upper valve of an oyster possessing an elongate 

 contour with an undulating surface, a crenulated margin, and exhibiting a 

 length of 33 and an approximate height of 60 millimetres. The adductor 

 scar marking is posterior, large and ovately lunate, while the crenulations are 

 composed of numerous equi-distant short plications which are represented as 

 well on the external margin, the remaining shell structure consisting of 

 extremely fine concentric laminae of growth ; the ligament region is not 

 preserved in this particular specimen but is well seen in some much smaller 



