Nomenclature of the Foraminifera. 387 



inner and convex on their outer face, and are arranged longi- 

 tudinally, not all on the same plane, but, with the exception 

 of the outermost folds (which are more nearly parallel), cross- 

 ing one another at the extremities of the coil at various angles. 

 The size of the folds gradually increases from within outwards, 

 but is subject to irregularities sometimes suggestive of periodic 

 constrictions or undeveloped segmentation. The whole fossil 

 is about -Jq inch long, and 3^0 in breadth and thickness. 



Shelled specimens of this kind are abundant in the Magnesian 

 Limestone of Yorkshire {" Lower Limestone," in an old quarry 

 beside an inn called the Hampole Inn), and in the Zechstein 

 of Germany at many places. It is this form which was 

 noticed by Geinitz under the name of Seiyula pusilla, and by 

 King as Foraminites serpidoides. 



§ III. These irregularly coiled varieties are accompanied by 

 others that have a more discoidal arrangement of the whorls, 

 which, in this case, fold over and over on one plane or nearly 

 80, making a flatter shell, more or less oval, and leading us as 

 it were to the regularly discoidal narrow-whorled form which 

 was described by one of us, in 1850, as a " SpirilUna^'' (in 

 King's ' Monograph of Permian Fossils,' p. 18). The speci- 

 men then referred to was from Tunstall Hill, near Sunderland; 

 others have been met with in the Lower Magnesian Limestone 

 of Langton, co. Durham, and elsewhere. 



§ IV. Another form of the same kind of shell as the first- 

 mentioned (§ II.) has thicker folds, arranged more flatly on 

 one plane, in an oblong coil, and enveloping one another on 

 their edges, but sometimes showing, on the flatter faces, parts 

 of the early whorls, and thus much resembling some Milioline 

 shells. This is especially abundant near the Hampole Inn 

 above mentioned ; and, judging from the section of a shell 

 given as fig. 19, in pi. 10 of Geinitz's ' Dyas,' we presume 

 that it is not wanting in Germany. Among the specimens 

 from Yorkshire, some of the Milioloid varieties become oval, 

 and even circular, dififering from the discoidal forms of Tr. 

 pusilla only in having thicker, broader, and fewer whorls. 



§ V. In 1856 one of us discovered numerous minute 

 " arenaceous " Foraminifera in the shelly sands of the Indian 

 seas, which presented in their contorted tubular forms the 

 required recent analogue of the Permian fossil. Although, 

 indeed, the majority of those first found have a tendency to 

 fold more irregularly than the then known fossil specimens, 

 yet others of the latter have since been abundantly met with, 

 in which the almost discoidal outer folds are disposed to pass 

 for a little way on one of the flatter surfaces of the shell, and 

 then return to their original plane, or even to pass round about 



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