GENUS NODOSARINA. 165 



being so strikingly similar as at once to suggest their close affinity, (notwithstanding 

 that they are referred by D'Orbigny to different Orders) ; and this affinity being distinctly 

 proved by the existence of a continuous series of gradational forms, in wliich the spiral of 

 Mabellina uncoils itself more and more, until its axis assumes the rectilineal direction of that 

 of Frondicularia. 



253. Affinities. — The relationship of the universally-rectilineal or slightly-curved Nodosaria 

 to the unilocular Lagena is extremely obvious; many forms oi Nodosaria being in all essential 

 particulars Layence, of which the segments that are successively formed by gemmation have 

 remained in continuity with each other. The intimate structure of their shells, moreover, is 

 precisely the same; and the surface-marking of the simple is often precisely repeated on the 

 composite forms. The Cristellarian or fiat spiral forms do not seem to graduate into any other 

 type, being (so to speak), the culminating group of the series to which they belong ; so that 

 it is only through its simpler or more elementary forms, that these are related to the genera 

 to which we have assigned a parallel rank in the family Lagenida. 



254. Geographical Distribution. — Under some or other of its protean forms, the Nodosarine 

 type is very generally diffused through the seas of various parts of the globe. Nearly all these 

 forms are well represented in the Rhizopodal Fauna of the Mediterranean (liv) ; and the 

 Adriatic Sea is particularly rich in them, Crialellarice being found there of large size, and in 

 greater variety and abundance than elsewhere, and Planidaria being almost peculiar to 

 that locality. The Nodosarines arc not so common in littoral deposits as they are in those of 

 moderate depth. 



255. Geological Distribution. — Not only can the Nodosarine type be traced back in geolo- 

 gical time to a very remote antiquity — as far even as the Carboniferous epoch — but its leading 

 varieties are recognisable in the earlier strata, as well as in a succession of later formations. 

 The Triassic clay of Chellaston has been shown by Messrs. Rupert Jones and Parker (lv), to 

 contain not merely typical representatives of the Nodosarian, Dentaline, Glandulinc, Linguline, 

 Vaginuline, Frondicularian, Flabelline, Marginuline, and Cristellarian forms, but also a number 

 of those connecting links between these, of which mention has been made in the preceding 

 pages. Similar varietal modifications present themselves in the Foraminifera of this type 

 from the Lias-clay of England and the Continent (see Bornemann, ' Liasformation, Gottingen'). 

 The clays of the Oolites also are rich in them ; and in the Cretaceous series we meet with a 

 peculiar abundance and variety of Nodosarine forms. In the remarkable development of the 

 Rhizopodal fauna which seems to have taken place at the commencement of the Tertiary 

 period, the Nodosarine type appears to have had its full share, at least as regards the 

 abundance of individuals and the large size they attained ; but we do not find any well-marked 

 new varieties. The Vienna Tertiaries present us with an almost complete sample of the entire 

 series ; and it is in those and in the Sub-Apennine Tertiaries that we find the largest specimens, 

 especially of the Cristellarian sub-type, that are anywhere to be met with ; the nearest approach 

 to these at the present time being afforded by specimens collected on the Abrolhos Bank. 

 From a comparison of the Rhizopodal fauna of the Siennese clays with similar recent collections 

 from various localities in the Mediterranean, it is concluded by Messrs. Rupert Jones and 

 Parker (liv) that those clay beds were deposited at a depth of not less than 40, and not 



