﻿LITUOLA. 



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In the collection of Carboniferous fossils formed by the Geological Survey of Scotland 

 are a few examples of a large nautiloid Foraminifer of unmistakably Lituoline characters. 

 They are by no means uniform in general contour and bear evidence of having under- 

 gone a certain amount of change from external causes. The specimen figured (PI. I, 

 figs. 8, 9) is perhaps the best of the set, and is probably in nearly its original condition 

 in form and structure. Others appear to have been subjected to lateral pressure, and 

 are of lenticular (biconvex) shape, whilst some few are merely casts, from which the 

 test has entirely disappeared. 



The finer specimens are perhaps the largest nautiloid Foraminifera of Carboniferous 

 age hitherto met with, some of them being more than one tenth of an inch in diameter. 

 The exterior surface of the test seems to have been a good deal worn, and the component 

 sand-grains, which are remarkably uniform in size, are very clearly shown. The rough- 

 ness and unevenness of its inner surface may be gathered from the appearance of some 

 of the casts. One of these, from a smaller individual of the same species is represented 

 in PI. I, fig. 9. The minute structure of the test has in some instances been perfectly 

 preserved by the completeness of the calcareous infiltration, and the transparent section 

 of such a specimen, under a high magnifying power (PI. I, fig. 11), shows the peculiar 

 tubular or cancellated ingrowths, which, partially or entirely filling the cavities of the 

 chambers, form what is known as " labyrinthic " structure. On the other hand, to the 

 same complete infiltration may perhaps be attributed the difficulty of determining the 

 nature of the general aperture. Depressions on the anterior face of the terminal segment 

 seem to indicate the existence originally of a number of irregular perforations of various 

 sizes ; and a compound aperture of this sort is consistent with the known tendency of the 

 Lituolida. 



The only Carboniferous species to which Lituola Bennieana bears any great resem- 

 blance, or with which it is likely to be confused is Endothyra crassa. The latter, 

 however, though larger than many of its congeners, is smaller and smoother in texture 

 than the Lituoline form ; it has also a much larger number of chambers, is more com- 

 pactly built, has the simple aperture of its own genus, and has no labyrinthic struc- 

 ture : an array of characters sufficient to distinguish the two under any ordinary 

 circumstances. 1 



The first specimens of Lituola Bennieana which came under my notice were obtained 

 by Mr. James Bennie the assiduous collector to the Geological Survey of Scotland, 

 whose name may well be associated with so fine a species. 



1 Since this h;is been in the printer's hands I have received a considerable supply of Lituola Bennieana 

 from Mr. R. Etheridge, jun., and it now appears that the species is comparatively common in the Mount 

 Lothian Quarry, where it is associated with Endothyra crassa. Further examination confirms the distinctive 

 characters above enumerated in all essential points, and seems to indicate that the labyrinthic structure 

 and cribriform aperture are the most generally reliable. But the labyrinthic or cancellated portion is often 

 only a thin layer lining the inner surface of the shell-wall, and to observe it satisfactorily it is necessary to 

 make horizontal sections very near the surface of the test. 



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