PLICATULA. 14] 
of the same. He admits, however, that P. Cotteaui is practically inseparable from 
P. radiola, d’Orbigny, and gives the name chiefly because it occurs on a different 
horizon. Peron considers that P. Cotteaui is distinct from P. inflata: after the 
examination of a large series of specimens of different ages I am unable to accept 
that view, especially in consideration of the large amount of variation which occurs 
in the very closely allied species P. gurgitis. P. inflata is distinguished from 
P. gurgitis by the fewer and more regular ribs and the fewer spines ; also by the 
ribs being absent or indistinct on the ventral part of the valves in large specimens. 
Some specimens of P. inflata, with more numerous ribs, approximate to certain 
examples of P. gurgitis which have fewer ribs than usual; this is more particularly 
seen in some examples from the Upper Greensand. 
Remarks——The number and strength of the ribs vary in different examples ; 
large specimens are sometimes almost smooth (e.g. Pl. XXVI, fig. 9). 
Since two forms were included by Lamarck under the name P. radiola, and 
since uncertainty exists as to which of them his name should be applied to, I follow 
Pictet, Renevier, and Campiche in retaining the name inflata given by Sowerby. 
Types.—P. inflata is from the Cenomanian near Cambridge ; the specimens 
cannot now be found. The type of P. spinosa, Mantell, is in the British Museum. 
Distribution.—Upper Greensand near Nursted and (Chert Series) of the Isle 
of Wight. Rye Hill Sand of Warminster. Chloritic Marl of Maiden Bradley and 
the Isle of Wight. Grey Chalk of Folkestone. Chalk Marl of Ventnor, Folkestone, 
Reach, Burwell, Haslingfield, Harlton, Speeton, ete. Zone of Holaster subglobosus 
of Hitchin, Totternhoe, Arlsey, Isleham, Burwell, Cherry Hinton, Fulbourn, 
Shelford, Louth, Witheall, Speeton, ete. 
I have seen no examples from the English Lower Cretaceous which could be 
definitely referred to this species, but Topley (1875) has recorded P. inflata from 
the Hythe and the Sandgate Beds. 
Pricatuta Barrorst, Peron, 1887. Plate XXVI, figs. 12—18. 
1846. Purcaruna pecrinorpes, A. BE. Reuss (non Sowerby). Die Verstein. der 
béhm. Kreideformat., pt. ii, p. 37, pl. xxxi, 
figs. 16, 17. 
1850, — noposa, A. d’Orbigny. Prodr. de Pal., vol. ii, p. 254 (partin). 
1872. _ — H#.B. Geinitz. Das Elbthalgeb. in Sachsen (Palzon- 
tographica, vol. xx), pt. i, p. 32, 
pl. ix, fig. 5. 
1878. — — ©. Barrois. Terr. Crét. des Ardennes (Ann. Soc. 
géol. Nord, vol. v), p. 391. 
