174 NEW YORK STATE MUSEUM 



which shows its oral termination occurs on shde i and this is much 

 larger than any other forms found. It measures 0.25 mm in length, 

 or more than double the usual forms. 



There is some doubt about this type; for it is not reported in 

 Paleozoic horizons as far as we know, and it is a type best developed 

 in Cretaceous and Tertiary formations. It has, however, been 

 previously reported from the Upper Trias of Derbyshire (Parker & 

 Jones) and is not rare in some of the Lias beds. 



Polymorphina communis (d'Orbigny) 



Plate 4, figures i, 2 



Guttulina communis d'Orbigny, 1826, Ann. Sci. Nat., 7:266, 



pi. xii, figs. 1-4; Module, no. 62 

 Guttulina communis d'Orbigny, 1846, Foram. Foss. Vienne, p 224, 



pi. xiii, figs. 6-8 

 Polymorphina communis Bagg, 1912, U. S. Geol. Survey Bui. 



513, p. 68, pi. xxi, figs. 13-15 (After Jones) 



In segmentation this form is closely related to Polymor- 

 phina problema (d'Orbigny), but the former is acuminate 

 at its oral end. P. communis has fewer chambers (usually 

 three or four), but many forms placed under this species do not 

 exhibit the contour and small segmentation the type demands. 

 I can not detect the Polymorphina aperture on the ultimate chamber 

 of the form seen on slide 3, which ought to appear if cut in median 

 section. There is, however, a very distinct irregularity on the 

 interior overlapping segments which is correctly, placed for this 

 feature and which we are confident is the indistinct or indefinite 

 structure of the pol^onorphine type. There should be more segments 

 if the form were P. problema, and they would be somewhat 

 more globose. The form is ver^^ minute and measures but o.io mm 

 in length and but 0.07 mm in greatest width. The rather deep 

 sutures observed in the cross section (figure i) are partly due to 

 the high magnification, 232 diameters, as compared with the larger 

 Tertiary type shown in figure 2 . 



Pol^^morphina communis has been reported from 

 early Jurassic (Lias) strata, but we are not aware of its having been 

 hitherto recorded in Paleozoic formations. 



The species also appears to be present on slide 5 (X), but the 

 aperture is not shown in the cutting. The aboral end is here a 

 little more extended than the type, but there are four overlapping 

 segments and the outline resembles this species. 



