MILIOLIDA. 3 
Characters.—Shell, convolute, planodiscoid, thin; the successive whorls becoming 
gradually, and often rapidly, wider; free from ornamentation, but marked with curved 
transverse lines of growth. Aperture, in full-grown specimens, a narrow slit, representing 
the open end of the coiled tube. Diameter 3th to ith inch. 
Cornuspira foliacea may be looked upon as the typical form of the genus. It is a 
beautiful, simple, little shell, inhabiting shallow seas, without much reference to latitude, 
and commonly attached by its flat surface to Algz or Zoophytes. Owing to the slightly 
bi-concave contour, dead specimens, somewhat worn, frequently have the thin central 
portions broken away; and it is in this condition that our Crag specimens were found. 
In the northerly British Seas it is an uncommon species; but on our South coast it is 
more frequent, and specimens in Mr. Jeffreys’ collection, dredged off Falmouth, are among 
the largest we know. Itiscommonin the Arctic Seas, in the Mediterranean, in the South 
Atlantic, and on the Southern and Western shores of Australia. We cannot trace the 
species further back in geological time than the Lower Tertiary formations; it abounds 
in the. Calcaire grossier, and may be found in almost every subsequent formation. 
Czjzek’s specimens were from the Miocene beds near Vienna, where Reuss has also 
obtained some varieties (C. angigyra and C. involvens). 'The specimens from the Crag 
were collected by Mr. Searles Wood, at Sutton, where they were found in considerable 
numbers, and of large size. 
2. CoRNUSPIRA INVOLVENS, Reuss. Plate III, figs. 52—54. 
OPERCULINA INVOLVENS, Reuss, 1849. Denks. Akad. Wien., vol.i, p. 370, pl. 45, fig. 20. 
— — Td., 1851. Zeits. Deutsch. Geol. Gesel., vol. iii, p. 73. 
CoRNUSPIRA a Td., 1863. Sitz. Akad. Wien., vol. xlviii, 1 Abth., p. 39, pl. 1, 
fig. 2. 
Characters.—Shell, free, convoluted, discoidal, bi-concave ; formed of a simple uncon- 
stricted, subcylindrical tube, wound on itself in one plane. Diameter about z,th inch. 
It is convenient to distinguish by a trivial name the thicker variety of Cornuspira, in 
which the tube, forming the spiral, retains to some extent the early, normal, cylindrical 
form, hollowed a little on its inner side, so that each successive whorl slightly embraces 
that preceding it.! On this ground we admit Professor Reuss’s specific term, though we 
attach no more than subvarietal value to the particular characters possessed by the 
specimens described. Professor Reuss records the occurrence of this form in the Baden 
Beds of the Vienna Basin, and at Offenbach and Hermsdorf, Prussia. 
1 Professor Williamson is probably quite right in describing his figure 201, pl. 7, of his ‘ Monograph,’ 
p. 91, as a young shell of C. foliacea, though it consists of ‘‘a few narrow rounded convolutions, of equal 
size,” &c. 
