GASTEROPODA. 3 



Our present specimen is not quite so large as the one figured by Brocchi, which is a 

 full-grown shell,, whereas the one now represented has not attained to maturity, and has 

 the outer lip sharp without denticulation on the inside of it. 



NASSA MICROSTOMA, S. Wood. 2nd Sup., Tab. I, fig. 4 a, b. 



NASSA MICKOSTOMA, S. Wood. Catal. Mag. Nat. Hist., 1842. 



PRISMATICA, S. Wood. Crag Moll., vol. i, p. 32, t. iii, fig. 6, 1848. 



ELEGANS, Dujard. Tr. Geol. Soc. Fr., p. 298, pi. xx, figs. 310, 1837. 



Spec. Char. Testa turritd, spird elevatd, costatd, costis 20 24, spiraliter striatd ; 

 anfractibus 1 8, qonvexis, suturis profundis, aperturd rotundato-ovatd ; labro incrassato, 

 intus denticulate ; labio superne uniplicato. 



Axis -fs of an inch. 



Locality. Cor. Crag? Boy ton. 



Fossil in Touraine, France. 



The specimen represented in the above figure is from the cabinet of Mr. Robert Bell, 

 and he tells me that it came from Boyton. Doubts occur as to whether shells from 

 this locality, not previously known in the Crag, belong to the Red or to the Coralline 

 Crag, 1 but I am inclined to refer our present specimen to the older formation, both from 

 the colour and appearance of the shell and from its apparent connections. 



I now consider this species as specifically distinct from prismatica, and probably the 

 same as the shell figured in Crag Mol., vol. i, PI. Ill, fig. 6, and which in my synoptical 

 list is inserted as Nassa prismatica var. limata. I refer it to A T . elegans, Dujardin, an 

 abundant Touraine shell which is much less than prismatica, has a greater number of 

 costee, and a smaller opening comparatively ; as it is quite distinct from the well- 

 established Red Crag species called N. elegans by the late Rev. G. R. Leathes in 1824, 

 while Dujardin's name of elegans bears a date of 1837, it is necessary to suppress the 

 latter to avoid confusion, and I have therefore assigned to it the name microstoma which 

 I used first in my catalogue of 1842 referred to. 



1 I have not been able to see the Boyton excavation open, but I am informed that a thin layer of Red 

 Crag is found there reposing upon a small thickness of Coralline, and the whole being inundated with 

 water the two are shovelled out together and washed for the phosphatic nodules, so that the specimens 

 from each bed are intermingled beyond possibility of distinction other than what may be drawn from the 

 appearance of the specimen or the character of the species. 



