NODOSARIN^. 57 



Dentalina communis, D' Orbif/ny- 



Under the name of Nadosaria [Dentalina) communis D'Orbigny has placed two varie- 

 ties of smooth, tapering, cui'ved Nodosurice, one having straight and the other inclined 

 septa. Both of these conditions (the septal planes being in one case at right angles to 

 the axis of the shell, and in the other oblique) occur together in very many specimens of 

 such Dentalina, and therefore can be accepted only as artificial means of distinction. 

 Moreover, the relative length and convexity of the segments are extremely vajiable, even 

 in one and the same specimen ; and the length, also, and curvature of the shell, and its 

 departure from the cylindrical form, are all unstable characters. It results that all these 

 varieties (almost as numerous as the individuals) can be grouped either under "Nodosaria 

 dentalina" of Lamarck, or the better known name "Dentalina communis," D'Orbigny. For 

 convenience, we may keep the oblique-chambered specimens separate from the others 

 when it preponderates over the other character. 



The modifications of the Dentalinte having straight septa are more numerous than the 

 others, as the latter, or oblique forms, soon become more definitely characterised as 

 ' ' Vagin ulin ce" and ' 'Mar (/in irlin ce." 



There are, however, other varieties of smooth Dentalince, many specimens having 

 globose chambers [D. radicularis, Miinster, &c.), and others having swollen but long 

 segments {D. (/lob if era, Batsch, &c.). 



These smooth Dentalina are really tapering and curved sub- varieties of Nodosaria 

 radicula ; the ornamented individuals belonging to N. raphanus ; and the obliquity of 

 the segments and departure from axial symmetry culminating in the closely coiled and 

 discoidal Cristellarice. 



Among the numerous Dentaline sub-varieties of Nodosaria raphanus {Dentalina 

 obliqua, Linn., being the first in order) every modification of N. raphanus has its Dentaline 

 representative, whether the riblets be general or partial, few or many, coarse or fine, 

 straight or oblique, continuous or interrupted, obsolete or replaced by spines or granules. 

 So also there are Vaginuline, Marginuline, Cristellarian, Trondicularian, and other modifi- 

 cations, respectively smooth (after the habit of N. radicula and its congeners), or orna- 

 mented (after any of the patterns adopted by N. raphanus in its variations). As Marginulina 

 raphanus is the central form of all these modifications of one type, we have chosen it (as 

 Nodosarina raphanus, typica) as the zoological representative of the group. 



It is inconvenient at present to construct a scheme of the alliances of the chief 

 Nodosarine forms ; and even for the Nodosaria alone it would be almost a vain labour to 

 attempt it, as they all mutually graduate one into the other — Glandinulina, Lingulina, 

 Dentalina, Vaginulina, Marginulina, &c., having full participation in all the characters 



8 



