76 CARBONIFEROUS AND PERMIAN FORAMINIFERA. 



TROCHAMMINA ANCEPS, nov. PI. Ill, fig. 8, a, b. 



Characters. Test free, convoluted, discoidal, thin, consisting of a spuriously septate 

 tube coiled in one plane. Septa marked externally by oblique slightly depressed lines. 

 Diameter ^jth inch ( 4 millim.). 



A variety closely allied to Trochammina incerta, or perhaps better regarded as a 

 transition form between the non-septate Tr. incerta and the segmented, almost Rotalian 

 Tr. inflata. The septation depends, as in all the subdivided Trocliammina, on the 

 infolding of the primary shell-wall, not on the successive formation of chambers, each with 

 its proper calcareous investment. It is a rare variety, and the specimens are nearly 

 always of small size. They are chiefly interesting from the intermediate position they 

 occupy. 



Distribution. Only noticed hitherto at a few localities in the higher Carboniferous 

 Limestone (Yoredale) beds of England, and in the Lower Carboniferous Limestone 

 Group of Scotland. 



TROCHAMMINA ANNULARIS, nov. PI. Ill, figs. 9, 10. 



Characters. Shell free, annular, spiral ; formed of two or three convolutions of a 

 non-septate tube. Convolutions irregular, seldom on one plane, but frequently more or 

 less superimposed vertically ; never commencing at the centre of the test, but leaving a 

 space of about one third of the whole diameter quite open. Tube apparently 

 twisted, especially at points in the earlier portion of its course. Diameter T^th inch 

 (0-17 millim.). 



A very minute variety, intermediate in its morphological characters to Tr. incerta and 

 Tr. ffordialis ; very rare, and, except that it is sometimes found with Tr. yordialis, 

 little associated with other members of the genus. The two figures, PI. Ill, figs. 9 and 

 10, drawn from different specimens, are fairly representative, the few examples which have 

 been found being very uniform in character. From their small size, and extremely fragile 

 nature, the specimens are probably often destroyed or washed away in preparing material 

 for examination, and even when retained they are liable to be overlooked. 



Distribution. In the Four-fathom Limestone, Elfhills, Northumberland, and in the 

 shale over No. 1, Limestone, Calderside, Lanarkshire. In both places rare. 



