McClung.] Microscopic Organisms of Upper Cretacious. 423 



Globigerina BULLOIDES. (PI. LXXXV, ff. 5-8.) 



Globigerina bulloides d'Orbigny, 1826, Ann. Sci. Nat., vol. vn. 

 Globigerina depressa Ehrenberg, 1854, Mikrogeologie, pi. xxvi, f. 92. 

 Rotalia rudis Ehrenberg, 1854, ibid., pi. xxiv, flf. 35, 36. 



"Test spiral, subtroclioid ; superior face convex, inferior 

 more or less convex, but with deeply sunken umbilicus ; per- 

 iphery rounded, lobulated ; adult specimens composed of about 

 seven globose segments, of which four form the outer convolu- 

 tion ; the apertures of the individual chambers opening inde- 

 pendently into the umbilical vestibule. Diameter sometimes 

 0.36 mm. but oftener much less." — Brady. 



Among the most widely distributed and oldest species of the 

 Foraminifera is G. bulloides. It is now present in such abun- 

 dance in the deep-sea ooze as to compose ninety-seven per cent. 

 of it. In the past it was equally as important an agent in the 

 formation of the great chalk beds. Being so universally dis- 

 tributed, it is subject to considerable variation in form and size. 

 In general, however, it may be stated that the chambers num- 

 ber from eight to sixteen, each being approximately spherical in 

 shape. The spiral, formed in the process of growth, consists of 

 groups of four, disposed in as many planes as there are groups. 

 In this respect the species was found to differ from the descrip- 

 tion of Brady given above. Coarse perforations pierce the shell 

 for the extrusion of the sarcode, and some forms have spinous 

 processes over which the body substance is extended. Each 

 chamber has a mouth opening placed in close relation to those 

 of the other chambers at the umbilicus, a point near the center 

 of the lower group of four. The shell may be thin and trans- 

 parent or thick and somewhat opaque, depending upon the size 

 of the organism and its habitat. A pigmy form also exists that 

 resembles the typical in everything except size. 



Globigerina spinosa, sp. nov. ( PI. lxxxv, f . 7.) 



Shell composed of about eight markedly globular segments, 

 the union between which is so slight that they appear as almost 

 independent chambers ; the last formed much larger than the 

 primordial one and the others of the first group of four. Wall 

 thick, coarse, and closely beset with strong, stout spines over 



