ENDOTHYRA. 99 



partially or entirely. Sometimes the surface of the chambers is nearly flat, and the 

 sutures are marked by excavated lines ; frequently the exterior of each segment is some- 

 what depressed or hollowed, and the septa are correspondingly raised. The edge-view, 

 PI. V, fig. 13 b, owing probably to superficial irregularity in the particular specimen, 

 gives the idea of a much thicker contour and much greater solidity than the variety 

 generally exhibits. 



Distribution. A rare form, whether in the number of localities or the frequency of 

 the specimens. Endotliyra macella has been found in the Yoredale rocks of Swaledale, 

 and the Upper Mountain Limestone of the Bristol district ; in the Lower Carboniferous 

 Limestone Group of Scotland, and in the Castle Espie shale, Ireland. 



ENDOTHTRA ORNATA, Brady. PI. VI, figs. 1 4. 



EKDOTHYRA ORNATA, Brady, 1873. Mem. Geol. Survey Scotland; Expl. Sheet 23, 



pp. 63, 95, &c. 



Characters. Test free, nautiloid, biconvex, rounded, nearly symmetrical bilaterally ; 

 composed of five or six regular convolutions, the last of which is alone visible on the 

 exterior. Segments numerous, 14 or more in the final whorl of fully grown individuals. 

 Sutures, showing as slightly limbate lines in immature specimens, as stout, irregularly 

 radiating costae in adults. Margin, sharp or carinate. Diameter, -^ inch (0'8 mm.). 



A handsome, strongly marked variety, the adult condition of which is well represented 

 in figs. 1 a, b, of Plate VI, as a lenticular, carinate shell, with stout, curved, irregularly 

 distributed, radiating costae. The strongly marked exogenous shelly growths impart to 

 the test its most striking character, and obscure all external indications of its interior 

 structure. In the young condition the septal lines are marked by slightly limbate bands 

 radiating from the umbilicus and nearly regular, as in fig. 2 of the same plate. The 

 horizontal section, from a medium-sized specimen, fig. 3, shows how regular the actual 

 septation is, and how uniformly radial in its direction, not set obliquely after the usual 

 manner of helicoid Foraminifera. With these features Endothyra ornata is easily distin- 

 guished from any other Carboniferous species. The two forms following next in order, 

 E. tenuis and E. obliqua, have some characters in common with it, which will be con- 

 sidered in their right place, the former of them is probably only a varietal modification. 



Distribution. In England, rare in the Lower, less rare in the Upper Carboniferous 

 Limestones ; in Scotland hitherto found in beds belonging to the Lower Carboniferous 

 Limestone Group only, and very rare therein ; occurs also in Ireland, in the Castle Espie 

 shale. 



