GENUS NODOSARINA. 159 



forms of Nodosarina, that they might readily be taken either for their young, or for fragments 

 of them accidentally disjoined ; and D'Orbigny states that he actually regarded them in this 

 light, until he found Layena abounding in localities from which Nodosaria was altogether absent. 



241. Geographical Bistributiou. — This generic type appears to be pretty widely diffused; 

 having been found in marine sands from the coasts of Great Britain and Norway, Bombay, 

 Singapore, Australia, and Patagonia ; and also in dredgings from great depths. Generally 

 speaking, the largest and most strongly marked Lac/eiue are found at an average depth of 

 about fifty (twenty-five to seventy-five) fathoms ; the more delicate varieties being either from 

 shallower or from deejjer water. 



242. Geological Distrihdion. — Large examples oiLagena present themselves in the upper 

 Chalk of Maestricht : but this type docs not commonly present itself until the Tertiary period, 

 when it is met with abundantly in tlic Grignon and Bordeaux beds ; also in certain Eocene 

 and Miocene beds of Germany. It occurs, but not abundantly, in the Vienna basin, in the 

 Sub-Apennine beds, at Baltjik, and in San Domingo. It is very large in the Crag of Suffolk; 

 and it abounds in the Post-Tertiary clays beneath the fens of Lincolnshire. 



Gems II. — Nodosarina (Plate XII, figs. 1 — 7 ; and Williamson, figs. 33 — 67). 



243. Under the generic designation Nodomriiia an extensive series of forms will here be 

 reunited, which have been grouped by D'Orbigny and the systematists who adopt his views, 

 not only under several distinct genera, but under three different Orders. The propriety 

 of this reunion lias been insisted upon by Messrs. Parker and Rupert Jones on several occasions 

 (liv, lv, lxxvi, Lxxviii) ; and although in adopting their views on this point I am chiefly 

 influenced by my knowledge of the thoroughness with which this group has been studied by 

 them, yet I feel it right to state at the same time that the results of my own observations, so 

 far as they go, are so completely confirmatory of theirs, as to leave in my mind no doubt 

 whatever as to the correctness of their conclusions. Moreover the extraordinary tendency to 

 variation which is exhibited by some of the commonest forms of this type, has been recognised 

 l)y several of the ablest systematists who have treated of it, such as LinntEus, Fichtel and 

 Moll, and Williamson ; the group being one in which, as in Miliola, it is easy enough to esta- 

 blish generic difl'erences when only a few strongly marked types ai'e contrasted, whilst it 

 becomes more and more difficult to maintain these, in proportion to the number of indivi- 

 duals compared, until at last the difficulty amounts to an impossibility. — It will be convenient, 

 for the sake of avoiding repetition, to state in limine that we regard as the two extreme forms 

 of this type the straight rod-like Nodosaria and the spirally-coiled Crisiellaria ; the remainder 

 either forming part of the series by which one of these continuously graduates into the other, 

 or being (so to speak) offsets fi-om some part of that series distinguished by some peculiar 

 varietal modification. 



244. History.- — Although the generic designations Nodosaria and Cristellaria were first 

 introduced by Lamarck (lix), yet numerous organisms of the type now Ijefore us had been 



