FORAMINIFERA. 1 29 



genus Involuting formerly placed among the Rotaline Foraminifera. 

 In Trochammina (fig. 29, e) the test is usually spiral, consisting of 

 one or many chambers, free or attached, and, though sandy, with 

 a smooth surface. It ranges from the Carboniferous to the present 

 day. Valvulina (fig. 34) also generally has a spiral shell which may 

 be free or attached, and is normally thick-walled, imperforate, and 

 sandy. Sometimes, however, the shell is porous and smooth, 

 and in other cases the sandy coating seems to be a mere en- 

 crustation on a calcareous and perforate shell, so that Valvulina 

 (which is by Brady included in the family of the Textularidce) may 

 be regarded as a transitional type between the series of the imper- 

 forate and perforate Foraminifera. The genus makes its first ap- 

 pearance in the Carboniferous of Britain, is 

 abundant in the Tertiaries, and is represented 

 in existing seas. In the Nodosinella of the 

 Carboniferous we have another curious type, 

 closely resembling the well-known Nodosaria 

 inform, but having a sub-arenaceous, imper- 

 forate test. A still more singular form is the 

 Stacheia of the Carboniferous, in which the 

 test is also sub-arenaceous and imperforate, 

 but grows parasitically upon foreign bodies, 

 in the shape of a crust composed of " an 

 acervuline mass of chamberlets " (Brady). 

 Lastly, there is a peculiar group of the Litu- 

 olidtB represented by the recent Cyclammina 

 and the extinct Loftusia, in which the test is 

 sandy, and the finely arenaceous shell-wall is Fig> 34> _ A> Valvulina pal . 

 irregularly cancellated, so as greatly to restrict <*otrochus, viewed in profile, 



° J . . 11 t^. an " enl arged 45 diameters ; b, 



the actual Cavities Of the Chambers. In Cj- The same viewed from below. 



clammina the shell is spiral and nautiloid, ter r Brady!)° us imestone ' 

 with numerous chambers arranged in an in- 

 volute series. In the singular genus Loftusia (fig. 35), from the 

 Eocene Tertiary of Persia, the test is fusiform, and may attain a 

 length of from two to three inches. As regards its internal structure, 

 the shell is composed of a spirally rolled lamella, the volutions of 

 which run in the long axis of the test, and which is of a sandy 

 texture and is much cancellated (fig. 35, b). The spaces between 

 the volutions of the primary lamella are intersected by obliquely 

 directed partitions, which are also cancellated in structure, and are 

 connected by numerous irregular vertical pillars. 



The genus Parkeria, which has commonly been referred here, 

 has been shown by recent investigations to be truly referable to the 

 Hydrozoa, and to be related to the existing Hydradinia. 



Coming next to the great series of forms which have usually been 

 vol. 1. 1 



