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 j^th to gth inch. 



Cornuspira foliacea may be looked upon as the typical form of the genus. It is a 

 beautiful, simple, Httle shell, inhabiting shallow seas, without much reference to latitude, 

 and commonly attached by its flat surface to Algse 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 om- 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. It is common in 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 ffrossier, and may be found in almost every subsequent formation. 

 Czjzek's specimens Avere 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, Eeuss. Plate III, figs. 52 — 54. 



Operculina involvens, Reuss, 1849. Denks. Akad. Wien., vol. i, p. 370, pi. 45, fig. 20. 



— — Id., 1851. Zeit.s. Deutsch. Geol. Gesel., vol. iii, p. 73. 



COBNUSPIRA — Id., 1863. Sitz. Akad. Wien., vol. xWiii, 1 Abth., p. 39, pi. 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 ^th inch. 



It is convenient to distinguish by a trivial name the thicker variety of Cornuspira, in 

 which the tube, forming the spii'al, 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, pi. 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. 



