AET. 6 FORAMINIFERA: POLYMORPHINIDAE — CUSHMAN AND OZAWA 6 



Tertiary and in the present seas. Similarly, it will be found that some 

 of the species of various genera that are highly ornamented or have 

 very characteristic shapes do not range widelj^, while smooth forms of 

 the same genera for the most part have very much greater ranges. 

 We have recognized this fact, and it is possible in our material to 

 indicate several groups under a single specific name with more 

 restricted ranges, but it was found very difficult to show these dif- 

 ferences so that they would be really of use to the worker in the 

 group. Some of these forms undoubtedly overlap in their characters, 

 yet those of given areas or formations may have minor characters 

 which are distinctive when the specimens themselves are studied. 



With the smooth Polymorphinidae, especially in the more primitive 

 species of GuUulina, the limits of variation are very difficult to defi- 

 nitely fix, and young stages are also usually perplexing. Forms that 

 seem distinct in two areas may have connecting forms which bridge 

 the gaps, and all are placed together. It will probably be possible 

 with intensive work on restricted areas to definitely fix the limits of 

 variation in different species much more clearly than can be done 

 at the present time. 



Microspheric and megalospheric forms, even in the same area 

 or formation, are often considerably different in certain characters, 

 and when the full characters of the two forms are known in each 

 species the distribution will probably be restricted. 



Some distributions as shown by well-defined species are very in- 

 teresting. Some of these are already v/ell known from other groups 

 of the foraminifera. There are, of course, many areas in which there 

 have developed specialized species, very restricted in their distribution 

 and characterizing that particular area or horizon. Many such 

 examples will be found in the species given here, and a few only need 

 be mentioned: GuUulina regina with a restricted Australian-East 

 Indian range, a very striking species difficult to mistake; Polymorphina 

 advena, Oligocene of the Mint Spring marl of Mississippi; P. alleni 

 of the Eocene of England; P. burdigalensis, Miocene of Europe; 

 P. complanata, Miocene of Nussdorf; P. cushmani, lower Eocene, 

 Midway of Texas; P. frondea, lower Oligocene, Gulf Coastal Plain of 

 the United States; P. frondiformis, Pliocene of Sutton, England; 

 P. longistriata, lower Eocene, Thanet beds of Pegwell Bay, England; 

 P. parallela, Pliocene of St. Erth, England; P. subrhombica, Eocene 

 of New Jersey. These are well-characterized species, and their 

 absence in other regions is due to restricted distribution and not to 

 being overlooked. Some interesting relationships of rather remote 

 regions have been noted. That the lower Oligocene of the Gulf 

 Coastal Plain and the Miocene and living faunas of the Australian 

 region are closely related has been often mentioned. The Plio- 

 cene and Recent faunas of the region of Japan and southern 



