GENUS LITUOLA. 145 



215. Affinities. — The most intimate relationships which this type possesses, appear to be 

 imdoubterlly those by wliich it is connected with the other members of its own truly arenaceous 

 family. Wc have seen how nearly its lower forms approximate to Trochammina ; and, we shall 

 see that some of its higher are no less closely related to certain varieties of Valmdina. But it 

 is curious to remark how many types, alike in the porcellanous and in the vitreous series, are 

 represented as to form by the varieties of tliis single genus. In their attachment by one 

 surface, the incompleteness of the shell on that side, the indefinitencss of their plan of growth, 

 and the irregularity of aggregation of their chambers, the lowest forms present a striking 

 parallelism to Nuhccuhirid ; whilst in proportion as the shell detaches itself and becomes 

 complete on both sides, it comes to I'esemblc in its nautiloid form and mode of growth the 

 " dendritine" PcnerojjJis, whilst its crozier-like form is the exact parallel of the " spirolinc" 

 Pcneroplis. The subdivision of the principal chambers by secondary partitions is an advance 

 in grade of development corresponding with that which marks the difference between Miliola 

 and Fahalaria, or between Fmeroplis and OrbicuHna. In its rectilineal mode of growth, the 

 '■ nodosarine" variety corresponds with the " articuline " varfety of Vvrli-hralina ; but there is 

 no member, either of the porcellanous or of the vitreous series, in which this plan of growth 

 is combined with subdivision of the chambers. The types of tlie vitreous series represented 

 by the several varieties of Lituola in plan of growth and in the form and place of the aperture, 

 are, as we have seen, Tnmcaf/dina by the most regular of the attached forms, NuuiuHina by 

 those free, symmetrical, nautiloid forms whose aperture is an elongated slit at the inner 

 margin of each chamber, and Nndomria by the straight forms with a verv convex septal 

 plane and central aperture. 



216. Geoffraphical Distribution. — The adherent or " placopsihne" varieties q{ Litiiohi, like 

 their congeners the Trocliawmincc, are inhabitants of our existing ocean, being chiefly 

 brought up from considerable depths in warmer seas ; the free " nonionine " forms 

 seem to be common inhabitants of the littoral zone of northern temperate regions ; the 

 labyrinthic " nodosarine" have been obtained from the neighbourhood of Rio Janeiro, whilst 

 the simplest forms arc world-wide. 



217. Geohfjical Di-sfribiition. — The " spiroline " forms of Liticola are the earliest of which 

 we have any knowledge ; a minute and simple specimen of this having been found in the 

 Triassic clay of Chellaston (lv). The " placopsiline" forms have been first noticed adherent 

 to shells of the Lower Oolite ; and in the Cretaceous period these come to be very abundant. 

 It was at this epoch that the Lituoline type appears to have attained its greatest development, 

 as w-e here meet with the nautiloid and spirolinc forms in their greatest number, size, variety, 

 and complexity. The " nodosarine " form first presents itself in the Miocene Tertiarics of 

 San Domingo and Malaga, and in the Pliocene of Tuscany ; in which last situation it attracted 

 the observation of the accurate Soldani, being figured by him (c, pi. xix, fig 92 z, and ci, ii, 

 ])1. 3, fig. cc) under the names of Ortlioceras, Trochiis, and Vermicidm. 



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