116 PROTOZOA. 



great sections, typified respectively by Textularia and Eotalia. 

 In Textularia itself (figs. 18, /, and 22) the test is generally 

 conical or wedge-shaped, and consists of numerous chambers 

 arranged in two alternate parallel series. Bigenerina is much 

 the same as Textularia, except that the last-formed segments 

 are disposed in a single and not a double series, and both 

 make their first appearance in the Carboniferous, the latter 

 being a common type in many formations, and being specially 

 abundant in the Chalk. Bulimina (fig. 18, n), dating from 

 the Trias onwards, consists of spheroidal segments which 

 progressively increase in size, and form an oblique spiral ; 

 while Cassidulina (fig. 18, m), ranging from the Miocene to 

 the present day, though truly biserial, is more or less com- 

 pletely rolled up, and may thus be regarded as an involute 

 Textularia. Lastly, Chrysidalina, dating from the Chalk, is 

 like Textularia, but is triserial. 



In the Eotaline series, the shell is typically composed 

 " of a succession of coarsely porous or globigerine segments, 

 arranged in a turbinoid spire, and communicating with each 

 other by a crescentic aperture situated at the junction of the 

 septal plane with the free surface of the convolution " (Car- 

 penter). Such a form of shell is exhibited, for example, by 

 Discorlina (fig. 13, c), which dates from the Chalk, and is 

 found living in our seas. Pulvinulina, with a spiral, usually 

 trochoid shell, differs from Discorbina in having a much more 

 finely porous shell. By the researches of Mr Brady, this 

 type has been carried back to the Carboniferous period ; and 

 it is thus one of the earliest representatives of the Eotalines. 

 In Eotalia itself (fig. 1 8, d), the test is also spiral and turbin- 

 oid, but its structure is more complex than in the preceding, 

 the shell-substance being compact and very finely porous ; 

 while each chamber is enclosed by a complete wall of its 

 own, and there are canal -like spaces between the two 

 lamellae forming each septum. In these respects, Eotalia 

 closely approaches the Nummuline type. The earliest Eo- 

 talice appear in the Chalk, but the genus attains its maximum 

 in the Tertiary period, and is well represented at the present 

 day. The approximation to the Nummuline type is further 

 manifested by Calcarina (fig. 1 7, B and c), in which the 



