Nigerian Eocene Mollusca. 27 



Volutospina conicoturrita, sp. nov. 

 PLATE 3, figs, i, 2. 



DESCRIPTION. Shell turbinate, conico-turreted, depresso-ventricose ; body- 

 whorl inflated and rather more than twice the length of the spire which 

 consists of six or seven volutions ; surface spirally and depressedly striated, 

 and longitudinally costated ; suture deep and encircled by a moderately wide 

 depresso-concave platform, with obliquely projecting, hook-shaped, equi-distant, 

 marginal spines furnished antero-laterally with an elongate opening ; marginal 

 spines succeeded anteriorly by a row of equi-distant, compressed tubercles 

 (absent in young shells) forming part of the widely distant longitudinal costae ; 

 aperture sub-crescentic, elongate, posteriorly horizontal, anteriorly constricted, 

 terminating in a short and widely notched canal, labrum horizontally costated 

 within, margin thin and not crenulated ; columella sinuous, twisted, closely and 

 spirally striated behind, but smooth in front, bearing three or more central, 

 oblique plications of which the basal is strongest ; a moderately thin callosity 

 overspreads the postero-frontal face of the body-whorl ; protoconch smooth, 

 obtusely apexed, comprising about 2^- deep and laterally depressed whorls. 



DIMENSIONS. 



Adult. Young. 



Alt. ... ... ... 62 ... 12 millimetres. 



Lat 36 ... 6 



REMARKS. This shell, which is of abundant occurrence, is characterised 

 by its prominent sutural platform and hook-shaped marginal spines, the tall 

 and distantly ribbed whorls of the spire with their flattened sides, together 

 with the presence below, in the adult stage, of a row of equi-distant, 

 compressed tubercles on the posterior region of the longitudinal costae. Wide 

 and deep avenues are formed between the longitudinal costae, while the entire 

 surface of the shell is more or less transversely and longitudinally striated, 

 the striations being less obvious on the central area of the body-whorl as also 

 that covered by the callosity. 



The spiral sculpture is composed of equi-distant, undulating flattened 

 circlets, possessing thickened and rather serrated posterior margins. There 

 appears to be no species with which to compare this shell unless it be 

 V. spinosa, Linnaeus^ a typical species of the Paris Basin Eocene and the 



