Lituola. _Lign. 111, fig. 3a._--In a young state the shell is nautiloid, as in _fig. 3b, 3d_; but becomes produced by age, and assumes a crosier-like form, as in _fig. 3a_. The cells are filled with a porous testaceous tissue, as shown in _figs. 3b, 3c_; which also illustrate the foraminiferous character of the shells in this class of animals; for both the external testaceous covering, and the septa of the cells, exhibit perforations.[321] [321] The perforations are omitted, by mistake, in the figure of the adult shell, _fig. 3a_. [Illustration: Lign. 112. Spirolinites in Flint. _Chalk. Sussex._ (_By the late Marquis of Northampton._) The specimens are only sections of the shells Imbedded in flint, and seen as opaque objects with a lens of moderate power. The small figures denote the size of the originals.] [Sidenote: SPIROLINA.] Spirolina. _Lign. 112._--The general form resembles that of Lituola: the young shell being a discoidal, involute, and becoming produced by age; but the internal structure is different; the cells are simple cavities. The chalk and flints of Sussex abound in these crosier-like shells, whose existence in the cretaceous rocks was first made known by my deeply lamented friend, the late Marquis of Northampton. The annexed lignograph, from drawings by his lordship, shows the form and structure as displayed by sections in fractured flints. Four species were named by Lord Northampton (see _Wond._ p. 32-5); but it is doubtful whether all the specimens belong to more than one species; the apparent diversity of structure may arise simply from the different planes in which the sections happen to have been made. Globigerina. _Lign. 109, fig. 1._--The shell is turbinated, the cells are spheroidal, and the last, or terminal one, has a semilunar aperture at the umbilical angle. Several fossil species abound in the Chalk and in the tertiary deposits; and many living species swarm in our seas. [Illustration: Lign. 113. Nonionina Germanica, × 290. A recent specimen of the body of the animal; the shell removed by acids. _From the North Sea, Cuxhaven._ (_M. Ehrenberg._) _a, a._--Naviculæ and other organisms in the segments of the animal.] Nonionina.--_Lign. 113._--A nautiloid shell, with simple cells; the last cell has a single narrow aperture placed transversely over the dorsal aspect of the spire. One species occurs in the chalk formation of Germany; several in tertiary deposits, and in the existing seas. The figure, _Lign. 113_, represents the body of the animal deprived of its shell, to illustrate the nature of certain fossils from the Chalk. [Illustration: Lign. 114. Foraminifera in Chalk and Flint. × ×. (_Seen by transmitted light._) Figs. 1, 2, 3, 6.--Different forms of Rotalia. 2.--Resembles the recent Rotalia stigma; Ehrenberg; from the North Sea, near Cuxhaven.