98 CARBONIFEROUS AND PERMIAN FORAMINIFERA. 



Characters. Test nautiloid, compressed, laterally unsymmetrical ; excavated at the 

 umbilicus, thin and angular at the periphery ; consisting of several convolutions, of which 

 but little more than the latest is visible externally. Segments very numerous, narrow. 

 Septation usually marked by lines of lighter colour rather than by superficial excavation. 

 Margin sharp, but little constricted at the sutures. Surface smooth. Diameter, -^ inch 

 (0'5 mm.). 



Adult specimens of this little nautiloid variety are sufficiently marked in their 

 morphological characters to be easily distinguished from their congeners. The same can 

 scarcely be said of small and immature examples, which it is often difficult to separate 

 from those of Endothyra globulus. The relationship between the two forms is, in point 

 of fact, exceedingly close ; but the smaller size, the sharp periphery, and more, the 

 numerous segments of E. radiata, are features of easy recognition in fully grown indivi- 

 duals. The peripheral view, PI. V, fig. 11 b, does not show so thin and sharp a margin 

 as many examples present, but it very well exhibits the unsymmetrical contour of the 

 segments, which is a character of some importance. 



Distribution. In England Endothyra radiata occurs with some frequency in both 

 the Lower and Upper Limestones ; in Scotland it is common in the Lower, and very 

 common in the Upper Carboniferous Limestone groups. In the Calcaire de Namur 

 of Belgium obscure specimens probably belonging to the species have been noticed. 



ENDOTHYRA MACELLA, Brady. PI. V, figs. 13, 14. 



INVOLUTINA MACELLA, Brady, 1869. Report Brit. Assoc., Exeter Meeting, pp. 379, 382. 



Characters. Test free, spiral, much compressed or complanate, oval or rounded, 

 somewhat irregular ; formed of a number of convolutions, of which the last only is visible 

 on the exterior. Segments numerous, embracing, often depressed or concave rather than 

 convex externally. Septation obscure, sometimes marked by excavated lines. Surface 

 rough, irregular. Diameter, -^ inch (1-3 mm.). 



Under the name Endothyra macella have been grouped a number of large, thin 

 outspread specimens, differing collectively from other members of the genus, but 

 which, were it not for their dimensions, might almost be regarded as starved or 

 otherwise emaciated individuals. Further observation may show that they represent 

 merely a depauperated condition of some other species, but for the present there is 

 nothing to demonstrate such a connection. The specimens have but few segments in 

 each convolution, and the test is often so rough as to conceal the general structure 



