﻿NODOSINELLA. 



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NODOSINELLA PRISCILLA {DttlOSOn). PI. VII, figS. 8, 9. 



Dentalina priscilla, Dawson, 1868. Acadian Geology, 2nd edit., p. 283, fig. 82. 



Characters. — Test slender, moniliform, formed of several more or less elongated cells 

 separated by only slight constrictions. Length (?). Diameter inch (0*64 mm.). 



I think I cannot be wrong in associating this little fossil with the other imperforate 

 imiserial Carboniferous Rhizopoda comprised in the group Nodosinetta. Dr. Dawson 

 states that he does " not feel at all certain as to its affinities, more especially as in the longi- 

 tudinal section it does not show true septal plates, but only slight constrictions at the 

 nodes." I am indebted to Dr. Dawson for authentic specimens, and have made them the 

 subject of careful examination. They fully confirm his view as to the extreme simplicity 

 of the organism, which seems to be nothing more than a tube of indefinite length, 

 constricted at intervals. The test is thicker than is usual in the true Nodosarina, and I 

 am convinced that the minute structure is more akin to that of Trochammina than to any 

 perforate type — the texture being, in fact, just that which Trochammina would assume 

 on a sea-bottom of white calcareous mud. At the same time I do not doubt that there 

 is a very close genetic relationship between these " Protonodosarice," if one may call them 

 so, and the analogous hyaline forms of later age. The septation of the sub-arenaceous 

 Foraminifera differs both in extent and character from that of the hyaline types. In 

 Trochammina, for instance, the animal may be monothalamous or segmented; in the latter 

 case the subdivision is the result of the mere infolding or constriction of the shell-wall, 

 or else of the investment of the individual chambers taking the form of tent-like coverings 

 placed one over the other. An interesting illustration is furnished by PI. VII, fig. 1 a, which 

 represents a specimen of Nodosinella digitata, the earlier half of which has no septa what- 

 ever, whilst the remainder is divided into three segments. In N. cylindrica the septation 

 is of the most variable and partial nature, and in N. concinna it is effected by the rapid 

 narrowing of the investment, without the interposition of any septal plate. 



I have found no specimens myself that can quite satisfactorily be assigned to Nodo- 

 sinella priscilla. Pig. 10 represents one out of a number of similar slender forms, both 

 Carboniferous and Permian, that in some degree resemble it ; but the test is thicker and 

 rougher, and the sutures more sharply defined. Such characters are more apparent in 

 dark-coloured fossils like the subject of the drawing than in the constituent organisms 

 of a pure white limestone ; but this specimen is probably referrible to N. digitata. 



Distribution. — " This little shell is very abundant on the surfaces of bed b, Windsor 

 [Nova Scotia, N. A., White Carboniferous Limestone], but always in fragments." — 

 Dawson, loc. cii. 



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