BeniarJcs on the Foraminifera. By Prof. T. Bupert Jones. 69 



constituents, although still of composite structure. Like Globigerina 

 and Oi'huUna, this Miliola becomes less calcareous, he remarks, in 

 brackish water. In similar degree, but under marine conditions, 

 Trochammina is less arenaceous than Lituola. 



Dr. Wallich * remarks on the difference in test-structure between 

 the coarse-shelled Difjiugia and the chitonous Arcella, being only 

 of siibspecijiG value, at most, in these Proteina, which he places 

 much higher among the Rhizopods than the Herpnematous Fora- 

 minifera. 



My friend Mr. H. B. Brady, F.E.S., states, in a letter dated 

 December 25, 1875 : 



" I think I have satisfactorily settled that the dentaliniform Foraminifera from 

 the Carboniferous rocks were all non-porous (' imperforate '), — that those from the 

 Permian were partly tnie Dentdina; (at Byer's Quarry) and partly imperfornte 

 (at Tunstall Hill); the specimens in the latter case are larger and have much 

 thicker shells. Many Palaeozoic forms (not LcutaUna;') are quite thin-shelled, and, 

 to all appearance, imperforate — neither ' porcellanous ' nor truly 'arenaceous.' 

 Endothyra is another case in point, — thin-shelled, never porous, and subarenaceous. 

 I believe some of these forms are really and truly the commencement of two series, 

 diflereutiating, on one side, into a porous (perforate), — on the other, into a truly 

 arenaceous (imperforate) line of organisms. The Carboniferous Vahulirui is an 

 analogous, smootii, imperforate species. 



" Involutina (Liassic) has sometimes a perforate undershell, though arenaceous 

 externally. I have some specimens beautifully perforate, but not one in a hundred 

 of tliose I have worked upon. I am convinced that it runs into Trochammina 

 incerta without any gap, though di.-tinct enough in the tuberculate thickened 

 forms. Indeed, the key to the relationshijj between the Arenaceous and the Per- 

 forate forms is to be found in the genera Trochammina, Valmdina, Endothyra, and 

 Textidaria. The labyrinthic condition of some Textularim links them with the 

 LHwAw''' 



On the Abrohlos Bank occur ValvuUnse with coarse-grained 

 shells, and ' others of the usual fine-grained consistence. Whether 

 the coarser specimens are Lituolse imitating Valvulina, or really 

 Valvulina} with unusually coarse shells, losing their customary 

 hyaline tissue altogether, it is difficult to say. So, on the con- 

 trary, as the older (fossil) Buliminse and TextulariiB are sandy 

 (^Ataxoiihragmium and Phcanium, of Von Eeuss), it may be sur- 

 mised that they were at first either persistently sandy and Lituoline 

 forms, or at most only partially " hyaline," as Valvulina j is now ; 

 and that they have since produced more and more hyaline shell 

 (less and less sandy), until their successors have ceased to take up 

 sandy materials until arriving at an adult or old stage. 



Of the two gigantic arenaceous Foraminifera, ParJceria and 

 Loftusia, it is stated that the latter, elongate and biconical, 

 shelled with calcareous cement and fine sand-grains, has a similar 

 relationship to AlveoUna and Fu&ulina that Trochammina incerta 



* ' Annals Nat. Hist.,' jMarch 1864. 



t Some of the Cretaceous Valvulina: are quite Buliminoid in asjiect. 



