GASTEROPODA. 67 



somewhat exceeds its transverse diameter ; it is moderately large, and wide at the base ; 

 the junctions of the whorls are strongly marked ; the encircling costae are large, closely 

 arranged, and very densely nodulated. Axis 8 lines, transverse diameter of the last 

 volution 6 lines. 



Locality. Minchinhampton Common, where it occurs in the coarse planking : it is 

 moderately rare. 



We have dedicated this species to H. Gomonde, Esq., of Cheltenham, who has kindly 

 allowed us the use of his collection of oolitic fossils. 



MONODONTA, Lamarck. 1801. 



Shell turbinated, aperture entire, base of the columella forming a tooth, with an 

 exposed umbilicus half surrounding it ; beneath the tooth is a longitudinal groove, the 

 edges of which are acute ; the outer lip is thick, striated within. 



MONODONTA LVELLII, Archiac. Plate XI, figs. 4, 4, b. 



MONODONTA LYELLII, Archiac. 1843. Mem. Geol. Soc. France, torn, v, t. 29, fig. 8. 



Bronn. 1848. Index Palseont., p. 742. 

 TUEBO LYELLII, D'Orb. 1850. Prod. Pale"ont., p. 301. 



M. Testa turbinatd, spird acutd, anfractibus (4) convexis, tricinctis; cingillis clatis et 

 nodulosis; nodulis approximatis, antrorsum concavis; anfractu ultimo ventricoso, cingillis 

 7 ornato, ultimo cingillo maxima et profunde crenulato; umbilico magno. 



Shell turbinated ; spire elevated, acute ; whorls (4) convex, encircled with three cariiias ; 

 carinse elevated and nodular ; nodules placed close together, and concave on their anterior 

 sides ; the last whorl ventricose ; encircling bands 7, the last being the largest and is 

 deeply crenulated ; the umbilicus is large. 



The markings vary considerably in this species. In some specimens the encircling 

 costae are nearly smooth, in others they are merely notched ; but the greater number are 

 distinctly nodulated ; the junctions of the whorls are deeply impressed ; and the entire 

 shell is very thick. 



Locality. This shell is abundant in the shelly beds near Minchinhampton ; the si 

 varies from a diameter of 1 line to 5 lines. In the Great Oolite, Eparcy (Aisne), France. 



MONODONTA IMBRICATA. Plate XI, figs. 3, 3 a. 



M. Testa parvd, conicd; spird acuminatd; anfractibus subplanis; striis imbricatis, 

 transversis (4) cinctis; anfraciu ultimo ad basin subangulato . 



