Nigerian Eocene Mollusca. 45 



Barton Beds of British localities. If anything it may be smaller, slightly 

 narrower, and possessing a greater number of spiral striations, although its 

 convex and varicosed whorls, general sculpture characters, formation of the 

 aperture with its wide and short anterior canal, the thinly callused and triplicate 

 columella showing the two lower folds as close together and distant from the 

 upper, together with the non-umbilicated base, all of which characters typify the 

 British species. Following Dr. Jousseaume the shell is recognised as belonging 

 to his genus, Bonellitia, which was founded on Cancellaria bonellii of Bellardi 

 (Mem. R. Ac. Sci. Torino, 1841, Ser. 2, Vol. 3, pi 3, figs. 3, 4, p. 248), from the 

 Mio- Pliocenes of Italy, a similar adoption having been favoured by M. Cossmann. 

 Bonellitia, according to its author, occurs also in Recent seas. An adult form of 

 the Nigerian specimens, which are well represented, measures 15 mm. in altitude 

 and 8 in diameter, whereas one of the largest British examples gives a length of 

 25 mm. and a diameter of 14 mm. The protoconch assumes a smooth and 

 rather mammillated appearance with few whorls, the actual summit or nucleus 

 being slightly depressed, agreeing well with M. Cossmann's Text-figure 5, 

 p. 33 in the " Essais de Paleoconchologie Compared," part 3, 1899. 



DISTRIBUTION. Lutetian to Bartonian, Britain and Europe. 

 OCCURRENCE. Cuttings Nos. i, 5, 6, 10, 12, 14, 15. 

 COLLECTOR. Mr. Kitson. 



Family CERITHIID^. 

 Exechestoma cossmanni, sp. nov. 

 PLATE 5, figs. 8, 9. 



DESCRIPTION. Shell short, conical, widely based ; whorls turriculate, about 

 eight or nine, sub-centrally projecting and angulate, deeply sutured, with 

 irregular, distant and deeply sinuated varices especially on the penultimate 

 and last volutions ; aperture roundedly sub-quadrangular, canaliculated at base ; 

 labrum excavated at margin but less so than the varices ; columella short, 

 callose, biplicate below ; sculpture exhibiting deeply sinuated, close, longi- 

 tudinal striations, large equi-distant, compressed tubercles, microscopically ridged 

 and striated beneath forming the sub-medium angulation of each whorl, basal 



