342 GASTEROPODA OF THE INFERIOR OOLITE. 



which it may be distinguished by its uniformly smaller habit, by its more 

 transverse shape, and by the fact that the longitudinal (i. e. radial) varices are 

 relatively larger and extend across the entire body-whorl. But, as noted by the 

 authors, the varices vary much in magnitude, so that in some specimens they are 

 nearly obsolete. Under these circumstances the shells are not easily distinguished 

 from Neritopsis, cf. decussata, Miinster. 



Although regarded by Morris and Lycett as a Great Oolite species, I am 

 somewhat doubtful of the occurrence of Neritopsis varicosa in the Great Oolite 

 of Minchinhampton. On the other hand, it occurs not unfrequently in the Oolite 

 Marl of the Cotteswolds, and more rarely in the Pea-grit. 



275. Neritopsis, cf. decussata, Miinster, 1844. Plate XXVIII, figs. 5 a, 5&, 5 c. 



1844. Natica decussata, Munst. Goldfuss, Petref. Germ., pi. cxcix, fig. 10. 



As a species from the Coral Rag. 

 1852. Neeitopsis decussata, Munst. D'Orbigny, Terr. Jur., vol. ii, p. 227, 



pi. ccci, figs. 8 — 10. 



The species described above (N. varicosa) gradually shades off into cancellated 

 forms such as those figured in the accompanying plate. I might also refer to 

 Neritopsis cancellaia, Moore ( c Quart. Journ. Geol. Soc.,' vol. xxiii, p. 548, pi. xv, 

 fig. 20), and to some of the forms described under N. Ouerrei, Heb. and Desl. (' Bull. 

 Soc. Linn. Norm.,' vol. v, p. 185, pi. i, fig. 4). Cancellated forms of this kind seem 

 to occur on more than one horizon. There are two specimens from the " Base- 

 bed " at Lincoln, one of which is figured in the accompanying plate. The aperture 

 is somewhat more angular on the columellar side than usual. 



276. Neritopsis incisa, sp. nov. Plate XXVIII, fig. 2. 



Description : 



Height ..... 12*5 mm. 



Width . . . . .16 mm. 



Shell transversely ovate-oblong ; spire extremely few-whorled and very low. 



Body-whorl relatively enormous, with a somewhat flattened posterior area. The 



ornaments consist of about ten or twelve extremely rugose radial ribs, irregularly 



developed and divided by deeply-cut sulci. These are decussated throughout by 



