96 CARBONIFEROUS AND PERMIAN EORAMINIFERA. 



all these particulars the British specimens coincide very well with the described Russian 

 species. The only difference seems to be the presence usually of a somewhat larger 

 number of segments in each convolution and the occasional filling up of the umbilical 

 depression by the extension of the ends of the alar processes of the chambers and the 

 thickening of the walls. There seems no reason for associating the species with the 

 genus Nonionina especially in the absence of any other member of the group in the 

 Carboniferous fauna. There is a very obvious resemblance between parallel modifications 

 of the two genera, and Endothyra globidus may be regarded as the isomorph of Nonionina 

 depressuJa, just as E. crassa is the isomorph of N. umbilicaf,ula. It takes a place in 

 the Endothyran series as the passage form between E. Bowmani and E. radiata, on 

 the one hand, and E. crassa, on the other. The test though thin and smooth appears 

 to be imperforate, and it sufficiently resembles the allied larger species to leave little 

 doubt as to the similarity of its intimate structure, although it is next to impossible to 

 lay down this character with entire certainty, so small are the specimens and so completely 

 infiltrated with subcrystalline material. The cast of the interior of an unusually fine 

 example, PI. V, fig. 9, illustrates very clearly the form of the animal inhabiting the shell, 

 and its segmentation. 



There is no hard line of division between E. fflobulus and E. radiata, but they bear 

 the same sort of relation to each other that we find amongst the modifications of many 

 other helicoid types, e.g., Cristettaria and Polystomella, which present one set of varieties 

 with thick rounded margin and another with sharp periphery. 



Distribution. The earliest appearance of Endothyra fflobulus is in the Calciferous 

 Sandstone Series of Scotland at which age it is rare ; but it is common in the Lower and 

 Upper Carboniferous Limestone Groups of that country, and in the Lower and Upper 

 Limestone beds of England. It occurs in the Calcaire de Namur of Belgium, and 

 M. d'Eichwald's specimens were found in a yellow clay from the Village of Sloboda in 

 the Government of Toula, Russia. 



which the sutural depressions have been bridged over at intervals, as occasionally observed in E. Bowmani. 

 The anomalous apertures would be less noteworthy in an arenaceous or subarenaceous species. 



I append M. d'Eichwald's description in the hope that some future student may be more fortunate in 

 his search for specimens than I have been. 



" NONIONIXA KOTULA. 



" Testa microscopica, subglobosa, subaiquUateralis, convexa, loculis 8 sensim magnitudine increscentibus, 

 apertura semilunari, facie antica subtiliter punctata, suturis simplice pororum serie instructis. 



" Hab. dans Vargilejaune carbonifere du gouvernement de Toula pres du village de Sloboda. 



" Le test, qui ressemble un peu a un Falvutina, a de ligne de hauteur et | ligne de largeur ; les 8 loges 

 a dos arrondi sont plus larges que longues, les sutures sont finement pointillees ; 1'ouverture de la derniere 

 loge est sernilunaire, etroite de la face anterieure, qui est au-dessus d'elle, est tres finement pointillee. 



" Le test est en general plus haut que large, par consequent un peu comprime" des deux cotes ; il 

 ressemble a 1' ' Alveolina prisca, qui en differe par ses loges divisees interieurement en cavites plus 

 nombreiises " (Op. cit., vol. i, pp. 349, 350, Esp. 22, pi. xxii, figs. 18, a, 6). 



