CARBONIFEROUS PERIOD. 97 



must have been fragile until it was completed, is seldom clearly shown upon 

 the fossils. 



It was apparently linear, extending the full length of the shell until 

 closed by a new longitudinal septum at each side, leaving only a new 

 centrifugal aperture at the middle, in line with the others. Volutions from 

 five to eight ; septa from twenty to thirty in the outer volution ; septa 

 nearly straight at their outer or external edges, but laterally undulating at 

 their inner edges, where they join the outer surface of the next volution 

 within, as may be seen in specimens that have had a part of their outer 

 volution removed by weathering ; the same defacement also showing por- 

 tions of the series of entrifugal apertures. The undulations of the inner 

 edges of contiguous septa are not usually parallel ; but the convexity of 

 the folds of each septum generally comes opposite that of the folds of the 

 next adjacent septum, which gives rise to a peculiar confused and complex 

 appearance of the septa in those specimens that have suffered erosion or 

 weathering of the outer volution. 



Dimensions very variable ; one of the more robust specimens in the 

 collections being one centimeter long and half a centimeter in diameter ; 

 another measures nine millimeters long and two millimeters in diameter. 



Fischer described another species, together with F. cylindrica (loc. cit), 

 under the name of F. depressa, which latter species Dr. Geinitz (loc. cit.) 

 recognizes from Upper Coal-Measure strata at Nebraska City, Nebraska. 

 Meek and Hayden have proposed the name F. ventricosa to include 

 certain robust fonns from the Coal-Measures of Missouri and Kansas (Proc. 

 Acad. Nat. Sci. Phila., 1858, 261), and Mr. Meek has described two other 

 species from a similar horizon in Califoi'nia under the names of F. rohista 

 and F. gracilis (Geological Sm-vey of California, paleontology, vol. i, 1864). 

 With due deference to the views of those able and careful paleontologists, 

 I feel bound to differ with them in relation to the propriety of a specific 

 separation of these forms. Long familiarity with this protean species, dis- 

 tributed over an extensive region, has served to convince me that all the 

 varieties referred to, including F. depressa Fischer, belong to one species 

 only. In Southwestern Iowa, where Fusulina is abundant in strata of the 

 Upper Coal-Measures, varieties prevail at certain localities respectively that 



7 F 



