MARYLAND GEOLOGICAL SURVEY 469 



segments, of which four form the outer convolution; the apertures of 

 the individual chambers opening independently into the umbilical ves- 

 tibule. Diameter, sometimes l-40th inch (0.63 mm.), but oftener much 

 less." Brady, 1884. 



This species is not uncommon in the Maryland Miocene. Its first 

 geological appearance dates from the Cretaceous epoch. At the present 

 time it exists in seas of all latitudes and at all depths. 



Occurrence. — Choptank Formation. Jones Wharf, Peach Blossom 

 Creek. Calvert Formation. Plum Point, Chesapeake Beach. 



Collection. — Maryland Geological Survey. 



Globigerina cretacea d'Orbigny. 

 Plate CXXXII, Fig. 3. 



Olohigerina cretacea d'Orbigny, 1840, Mem. Soc. geol. France, vol. iv, p. o4, pi. iii, 

 tigs. 12-14. 



Description. — Test rotaliform ])ut strongly depressed; superior sur- 

 face flattened or but slightly convex, inferior side depressed tovi^ard the 

 center and excavated at the umbilicus; periphery obtuse and lobulated ; 

 shell typically composed of three fairly distinct convolutions; the outer- 

 most consisting of from five to seven segments, the later relatively small, 

 subglobular; the aperture opening into the umbilical vestibule. 



This species, vv^hich is most abundant in the Cretaceous deposits of Uie 

 globe, is very rare in our Maryland Miocene. Brady in the Challenger 

 Eeport states that he never found typical forms of this species in any 

 localities examined by the Challenger, but a few stoutly built modifica- 

 tions exist. 



Occurrence. — Calvert Formation. Chesapeake Beach. 



Collection. — Maryland Geological Survey. 



Family TEXTULARID/E. 



Genus TEXTULARIA Defiance. 



" The shell of Textularia essentially consists of a binary series of seg- 

 ments arranged symmetrically on the two sides of a longitudinal axis; 

 the segments of one side alternating with those of the other, and each 

 segment communicating with tlie segments anterior and posterior to it 



