Nomenclature of the Foraminifera. 297 



white*, opake, non-tubuliferous, calcareous-shelled Rhizopoda. 

 As in some groups of the hyaline Foraminifera, the shell is here 

 principally composed of siliceous sand, the shell-matter being 

 only in sufficient quantity to serve as a cement for the sand- 

 grains. 



Lituola, in its simplest form, is a mere string of suboval, suc- 

 cessively enlarging chambers, more or less irregular in outline 

 {Reophax Scorpiur us, ^lontiort). A similar, but attached, series 

 of plano-convex chambers (the lower face being often imperfect) 

 has been described as " CEufs de MoUusques " by Coruuel (Mem. 

 Soc. Geol. France, 2 ser. iii. pi. 4. f. 36). These latter often 

 have a more or less coiled set of commencing chambers ; and 

 then we have the Placopsilina Cenomana, d'Orb. (Rcuss, Abhandl, 

 Wien, vii. p. 71, pi. 28. f. 4, 5). These fixed Placopsiliue forms 

 are often wild in their growth, spreading and bifurcating with 

 great irregularity and to considerable extent (as much as an inch 

 in length sometimes) ; simple Nautiloid forms also occur fixed 

 [Lituola nautiloides, Schroeter, sp., Ann. Nat. Hist. 3 ser. iii. 

 p. 482). In a free state we find numerous Nautiloid symmetrical 

 Lituola, of small growth, such as we have already characterized 

 in Ann. Nat. Hist. 2 ser. xix. p. 301, under the name of Pla- 

 copsilina Canariensis, d'Orb. sp., from Norway. A smaller and 

 flatter form is figured by Prof. Williamson (Monogr. p. 34, pi. 3. 

 f. 72, 73) under the name of Nonionina Jeffrei/sii ; this is com- 

 mon on the British coasts, and indeed is of wide distribution. 



This Nautiloid form of Lituola is succeeded by crozier-shaped 

 forms, such as the so-called Spirolina aggbitinans, d^Orb. For. 

 Foss. Yien. pi. 7. f. 10-12, and the " Spirolinites " so common 

 in the Chalk. Many of the larger of these latter have their 

 chambers subdivided. 



The septal opening varies in the different above-mentioned 

 forms, from the simple roundish passage, or Nonionine slit, of 

 the arrested varieties, to the oblong, lobed, jagged, or compound 

 apertures seen in the more typical free shells. 



Lituola nautiloidea, Lamarck, is a well-developed crozier- 

 shaped shell : it has its chambers subdivided throughout ; and 

 its round or oval, and slightly convex, septal plane is pierced 

 with many passages. It is very common and large in the 

 Chalk. 



* In the living state, Orbitolites, Peneroplis, ancU ZpeoZma (members of 

 the "opake" f^roup of Foraminifera) have their shell-substance ])ink or 

 reddish, the milky whiteness of the dead shells being the result of bleach- 

 ing. This appears also to be the case with regard to Lituola ; as many 

 recent specimens have a reddish or ferruginous appearance, although their 

 constituent sand-grains are in themselves colourless. Prof. Williamson 

 has noticed a simdar condition in other Foraminifers (Monogr. p. G5). 



Ann. &; Mag. N. Hist. Ser. 3. Vol. v. 20 



