EXDOTHYRA. 101 



that species can be the result of pressure or other force acting from without, or indeed 

 can be other than morphological variations in the ordinary sense. The trivial name 

 originally given to specimens in Mr. Charles Moore's collection has therefore been 

 retained, pending more satisfactory evidence as to the zoological value of their conspicuous 

 characters. The salient peculiarity of Endotjii/ra obliqua is the relation of the axis of the 

 test to the spiral band of chambers. In the other Endothyra the axis of the spiral is 

 the shortest diameter of the test ; in the present species it is either directly or obliquely 

 through the long diameter, and the spiral, instead of being round, is oval or compressed. 

 A reference to the figures (PI. VI, figs. 5, 6) will do more than many words to explain 

 these structural features. A similar change in the relation of the axis to the body of the 

 shell is observable in many other genera of Foraminifera, and something approaching a 

 parallel to Endotlyra obliqua may be found in such species as Biloculina coniraria, 1 or in 

 the curious modification of Tejctularia named by d'Orbigny Citneolina pavonia? 



Distribution. Hitherto Endothyra obliqua has been observed in but few localities, 

 though it is by no means an uncommon form where it does occur. In England it 

 appears in both the Lower and Upper portions of the Carboniferous Limestone Series ; in 

 Scotland it seems limited to the Calciferous Sandstone or lowest division ; in Ireland it 

 is associated with allied species in the Castle Espie shale. 



ENDOTHYRA SUBTILISSIMA, nov. PI. VI, fig. 9. 



Characters. Test free, nautiloid, complanate, flat or only slightly convex ; composed 

 of a few regular convolutions rapidly increasing in width, the last almost entirely enclosing 

 the earlier ones. Segments, about seven or eight in the outermost or visible whorl. 

 Sutures and margin limbate. Periphery blunt, somewhat rounded. Surface granular, 

 especially at the umbilicus. Diameter, 7*5 inch (0'34 mm.). 



A very pretty and neatly made variety, with some primd facie likeness to the 

 Planorbulina (Planulina) Ariminensis of d'Orbigny. As far as can be made out, how- 

 ever, from the single example I have had to work upon, the test is imperforate and the 

 shell-texture precisely that of the smaller Endothyra, so that it may safely be regarded 

 as another instance of the isomorphism of which almost every modification of the 

 Endothyran type furnishes an example. 



Distribution. I know of only a single specimen, that from which the figures are 

 drawn, which was found by Mr. Robertson in the rich Lower Carboniferous shale 

 of Brockley, in Lanarkshire. It is not the only case in which my friend Mr. Robertson's 

 quick eye has detected minute inconspicuous forms that have escaped the notice of other 

 observers. 



1 Toram. Foss. Vienne,' p. 266, pi. xvi, figs. 46. 2 Ibid., p. 253, pi. xxi, figs. 5052. 



