Nigerian Eocene Mollusca. 15 



whorl. In its single digitation and prominent notch it somewhat resembles 

 RimeJla, although differing considerably in form, while the posterior canal in that 

 genus, instead of extending along the sutural region of the body-whorl, is 

 perpendicularly attached to the spire and sometimes nearly reaching the summit, 

 as in R. rimosa (Solander) from British and European Eocene deposits. The 

 pyramidal spire fits well into the sunken, sutural cavity of the body-whorl, while 

 the walls of the latter show a swollen character at the periphery, as well as a 

 depression in its dorso-median region. The three whorls following the smooth 

 nuclear volutions are prominently ornamented with numerous longitudinally, 

 obliquely curved costae and strong spiral bands, whereas the next and penultimate 

 whorls are restricted almost entirely to the spiral and vertically striated sculpture. 

 Broad and distant varices are observable on the more sculptured portions of the 

 spire, although much less obvious on the latter whorls. The sutural tabulation 

 of the spire is often scarcely perceptible in younger forms of the species. Less 

 developed and more delicately tested forms of this species are quite numerous, in 

 which the sutural platform of the body-whorl is insignificant, the labrum thin and 

 delicate not margined, being also without the digitation, while the callosity is 

 only feebly indicated and not raised or thickened as in adult examples. The 

 shell, admirably preserved, occurs in great profusion in Nigerian deposits, 

 although only a few specimens show a complete anterior canal, and then only is 

 this preserved in moderately young examples. Tubes of a small Serpula and 

 other organisms are sometimes found adherent to the shell, chiefly in the region 

 of the aperture. 



OCCURRENCE. Cuttings Nos. i, 2, 5, 6, 10, n, 12, 13, 15. 

 COLLECTORS. Sir F. Lugard, Sir J. Eaglesome and Mr. Kitson. 



Semiterebellum suturocostatum, sp. nov. 

 PLATE 4, figs. 14-17. 



DESCRIPTION. Shell narrowly conical, depresso-convex ; body-whorl com- 

 presso-convex, unidigitate, longer than the spire ; spire narrow, produced, 

 consisting of 6 or 7 whorls, of which 2.\ constitute the smooth protoconch, whorls 

 nearly on the same plane ; suture margined with a row of nearly contiguous, 

 short, thick, slightly oblique costae, divided in the centre by an impressed line ; 

 aperture narrowly elliptical, notched at base, terminations canaliculated, anterior 



