Nigerian Eocene Mollusca. 23 



DIMENSIONS. 



Adult. Young. 

 % Alt. ... ... ... ... 43 ... 19 millimetres 



Lat. ... .... ... ... 20 ... 9 ,, 



REMARKS. Most of the characters of this species are drawn up from an 

 adult form, younger examples having a plainer and smoother periphery on the 

 latest whorl, while the spiral striations on the posterior surface of the volutions 

 are more distinct than the sinuous lines that cross them. This shell differs from 

 S. ingens by its smaller size and more complicated sculpture, although the 

 sinus is relatively as deep and presents similar features of detail but on a 

 smaller scale. The species is fairly common, quite a number of examples 

 having been found in the Nigerian deposits. 



OCCURRENCE. Cuttings Nos. i, 5, 6, 10, 12, 15. 

 COLLECTORS. Sir J. Eaglesome and Mr. Kitson. 



Eopleurotoma nigeriensis, sp. nov. 

 PLATE 2, figs, n, 12. 



DESCRIPTION. Shell fusoid, conically acuminate, spire of same length 

 as body - whorl ; volutions n or 12, depresso-convex, strongly costated longi- 

 tudinally and spirally striated, posteriorly narrow and only half the depth of 

 the anterior part of the whorl ; body-whorl moderately inflated, canaliculated, 

 and slightly twisted at termination where a thin umbilical slit is present ; 

 columella nearly straight, covered with a smooth callus which is thick and 

 elevated at the posterior end, thin in the centre and afterwards thickening to 

 the termination in front ; outer lip moderately thin, with a curvature towards 

 the front, margin slightly serrated, furnished with a widely rounded, or sub- 

 triangular sinus at the shoulder ; aperture narrowly oval, canaliculated ; sculpture 

 exhibiting numerous, thick, spiral lines crossed by about thirty equally 

 strong, longitudinal ribs which are obliquely inclined anteriorly but more or 

 less vertical on the narrow or posterior division of the whorl, thus forming a 

 sub-triangular bend which gives rise to the sinuation ; minute nodosities mark 

 the junctions of the costae. 



DIMENSIONS. 



Alt. ... ... ... ... ... 44 millimetres 



Lat 13 it 



