FORAMINIFERA. 



Genus FUSULINA, Fischer. 



Fusulina robusta, Meek. 



PI. 2, Fig. 3, and 3 a, b, c. 



Shell oval-subglobose, the longer diameter being to the shorter 

 abont as 26 to 20. Surface with longitudinal linear, slightly 

 impressed furrows, placed at regular intervals, one over each 

 septum, and extending from end to end, — becoming a little 

 twisted as they approach the extremities. Volutions five or six, 

 the last or outer one being usually less capacious than one or 

 two of those immediately within. Septa about thirty to forty in 

 the last or outer turn of adult shells; nearly straight at their 

 outer edges, but becoming waved and distorted within, so as to 

 give the interior a complex cellular appearance, particularly near 

 each end of the shell. Mesial fissure apparently short and very 

 narrow or linear. 



Greatest length of one of the largest specimens, 0.40 inch ; 

 breadth of do., 0,32 inch. Average size, about one-fourth less. 



Compared with the published figures of the Eussian species, F. cylindrica of 

 Fischer, this species will he found larger and greatly more ventricose. Notwith- 

 standing its larger size, however, it usually has about one volution less, while its 

 septa, and the coincident striae of the exterior, are less numerous and more 

 distant. It agrees more nearly in form and size with a variety of a shell found 

 in the Coal-measures of Kansas and Missouri, — usually referred to F. cylindrica, — 

 for which Dr. Hayden and the writer proposed the name Ventricosa. (Proceed. 

 Acad. Nat. Sci. Philad. 1858, p. 2G1.) It is uniformly much more gibbous, how- 

 ever, and generally attains a larger size ; while transverse sections show that even 



(3) 



