FORAMINIFERA OF THE ATLANTIC OCEAN 53 



annular chamber not connecting with each other but with those 



of the adjacent preceding and succeeding annular chambers; wall 



imperforate except in the very earliest chambers which are perforate; 



apertures numerous, rounded on the periphery of the test. 



Eocene. 



Genus OPERTORBITOLITES Nuttall, 1925 



Opertorbitolites Nuttall, Quart. Journ. Geol. Soc, vol. 81, 1925, p. 447. — 

 CusHMAN, Special Publ. No. 1, Cushman Lab. Foram. Res., 1928, p. 

 223. 



Genoholotype. — Opertorhitolites douvillei Nuttall. 



Test circular, lenticular, consisting of a median chamber-layer 

 resembling that of Orhitolites with a thick imperforate lamina of 

 shelly material on each side of the median layer. 



Eocene. India. 



Genus CRATERITES Heron-Allen and Earland, 1924 



Craterites Heron-Allen and Earland, Journ. Linn. Soc. Zool., vol. 35, 

 35, 1924, p. 611. — Cushman, Special Publ. No. 1, Cushman Lab. Foram. 

 Res., 1928, p. 223. 



Genoholotype. — Craterites rectus Heron-Allen and Earland. 



Test probably attached in life, the whole composed of numerous 

 layers of chambers, the basal layer without trace of spiral develop- 

 ment, form in side view contracted above the base, and the outer 

 end broadening and convex; chambers very numerous; wall calcare- 

 ous; outer surface with numerous small rounded openings. 



Recent. South Pacific. 



Family 27. ALVEOLINELLIDAE 



Test imperforate except the proloculum and second chamber; 

 general shape of the test fusiform, coiled about an elongate axis; 

 chambers completely involute, divided into chamberlets; apertures 

 numerous, in one or more rows on the face of the last-formed chamber. 



The foraminifera belonging to this family are highly developed, and 

 have probably been derived from such forms as Peneroplis by the 

 division of the close-coiled forms into chamberlets and an elongation 

 of the axis. Some of the Eocene species of Borelis are much com- 

 pressed in the line of the axis and for the exception of the division 

 into chamberlets are close to Peneroplis. The greatest development 

 of the family seems to have been in the Eocene when they were 

 widely distributed in both the Eastern and Western Hemispheres. 

 With the exception of a single small species of Borelis, the distribution 

 of the family in the present oceans is mostly confined to the Indo- 

 Pacific where large specimens are often very abundant in shallow 

 warm water of coral reef regions. 



