86 CRETACEOUS GASTROPODA 
There are only three species known living, and for the Fulg. dubia H. and A. 
Adams propose the sub-genus <Awrinia, although there seems to be scarcely a 
necessity for this, when the number and form of the columellar plaits actually 
varies in one and the same species, as appears to be the case. 
The two species which we describe here under Fulguraria do not differ as 
regard form and ornamentation in any way from Fulg. fulgura, and they are both dis- 
tinguished by the sharpened anterior margin of theinner lip. In the living species, 
the inner lateral flattening and the central thickening of the inner lip is by no 
means so clearly developed, but it is distinctly indicated, and its form in the fossil 
species can be compared only with that of the living Fulgurarie. 
One of the species here described, the Mulg. elongata, D’Orb., has only three 
nearly equally strong columellar plaits, and the other, Hulg. multistriata, n. sp., has 
four, three of which are stronger and the last posterior less oblique. This—the 
number of columellar plaits—can hardly be said to be a generic difference between 
the fossil and living species. I have for that purpose compared numerous specimens 
of the living Pulg. fulgura, and I find that there is a good deal of variation to be found 
in the form and number of plaits, although I never found them to be less than five. 
Some specimens have distinctly three principal folds ; out of eight the two anterior, one 
between the first and second principal, and two behind the third being considerably 
thinner; sometimes there are three smaller posterior and one between the second and 
third principal, so as to raise the number of columellar plaits to nine or ten. Other spe- 
cimens have the two first anterior small, the third is the strongest and more distant 
from the others, which amount to from two to five, becoming gradually thinner 
towards the anterior termination. Considering these changes of the plaits on one side 
and the great similarity of the entire shell on the other, I believe that the fossil 
forms ought not to be generically separated, for they must be regarded as the true 
cretaceous representatives of Fulguraria. 
Another point, which may be thought of great importance, is the thickening 
of the posterior margin of the outer lip, its partial insinuation and a corresponding 
curve of all the strize of growth below the suture. On account of this character the 
Fulg. elongata has been determined by Rémer and others as Plewrotoma, and in some 
respects it recalls Borsonia. The insinuations of the strie of growth may be, how- 
ever, readily observed in the living Fulguraria fulgura too, and they are inseparably 
connected with the posterior constriction of the whorls; the difference consisting 
merely in the strive being only a little more strongly developed near and at the 
margin of the aperture in large specimens of Fulg. elongata, than they usually are 
in Fulg. fulgura. . 
There are only very few tertiary species, which appear to belong to Pulguraria, 
but a good many of the cretaceous forms may be attributed to this genus, although 
they certainly require first a careful comparison as to their characteristic affinities with 
Fulguraria. We may mention Mitra Murchisoni, Miller. (Petref. Aachner Kreidef. 
1851, IT, Pl. III, Fig. 23), if it be really different from the Pulg. elongata, D’Orb., 
. about which serious doubt must be entertained; Volut. Navarroensis, Shumard (Gabb, 
