MARYLAND GEOLOGICAL SURVEY 475 



Cristellaria wetherellii (Jones). 

 Plate CXXXII, Fig. 16. 



Marginulina wetherellii Jones, 1854, Morris's Cat. Brit. Foss., Ed. 2, p. 37. 

 Criatellaria wetherellii Brady, 1884, ChaL Rept., vol. i.v, p. 537, pi. c.viv, tig. 14. 

 Cristellaria wetherellii Bagg, 18i)8, Bull. Amer. Pal., No. 10, p. 21. 



Description. — Test elongate, compressed, pod-like, primordial seg- 

 ments more or less involute, ultimate segments extending into a straight 

 or nearly straight series. The surface of the shell ornamented externally 

 by raised tubercles more or less regularly arranged between the septal 

 lines of some of the chambers and also upon the septal lines. Transverse 

 sections are elliptical and show in some forms an angular periphery and 

 when so they approacli Cristellaria decorata Eeuss in outline. 



Occurrence. — St. Mary's (?) Formation. Crisfield well (776 feet). 



Collection. — Maryland G-eological Survey. 



Subfamily POLYMORPHIN/E. 



Genus POLYMORPHINA d'Orbigny. 



The genus Polymorphina shows remarkable variation in its biserial 

 arrangement of lageniform chambers. Usually the segments are ar- 

 ranged somewhat oblique to the principal axis and the segments are pro- 

 longed and overlap each other in such a manner as to render the whole 

 shell very unsymmetrical. Sometimes the chambers are flattened, at 

 other times they are nearly round and their surface decoration is 

 equally varied. 



The genus is closely related to Textularia in its method of growth, but 

 it also presents strong affinities to Uvigerina and Nodosaria. The aper- 

 ture is typically a radiating fissure. 



It is most common at the present time in shoal waters and is known in 

 waters of the arctic, temperate and tropical zones. Its earliest appear- 

 ance as a fossil is in the Trias and it is especially plentiful in Tertiary 

 strata. In the Maryland Miocene, however, it does not seem to be at all 

 abundant and but few specimens occur. 



