12 PROCEEDINGS OF THE NATIONAL MUSEUM vol.77 



of the species given by Fornasini are evidently a Marginulina} Two 

 species of Dirnorphina described from the Vienna Basin by d'Orbigny 

 are also Marginulina with coiled chambers in their early stage. 



Therefore Dirnorphina is a very uncertain genus. We have a few 

 specimens having the early chambers arranged in a quinqueloculine 

 or somewhat triloculine series, later becoming uniserial. Such forms 

 correspond somewhat with the supposed Dirnorphina, but provi- 

 sionally we have included them in Pseudopolymorphina, from which 

 they are undoubtedly derived by adding chambers in a uniserial 

 arrangement. 



Dirnorphina compada described by H. B. Brady, Parker, and Jones 

 from the Crag of Sutton is an arcuate species resembling Marginulina. 

 It does not belong to the Polymorphinidae. 



In the following is summarized the evolution of the Polymor- 

 phinidae from the standpoint of the changes in arrangement of the 

 chambers. 



1. Some doubtful species of the Polymorphinidae are recorded from 

 the Palaeozoic as far back as the Ordovician, but undisputed species 

 belonging to the family are known only from the Triassic and later 

 formations. 



2. The Polymorphinidae are undoubtedly derived from some coiled 

 form of the Lagenidae such as Marginulina or Vaginulina by intro- 

 ducing a spiral arrangement of chambers. The family may be divided 

 into the following groups based on the differences in the arrangement 

 of the chambers: 



a. Chambers arranged in a spiral series added in planes less than 90° apart 

 from one another, each succeeding chamber removed farther from the base. 



Eoguttulina. 



This group is the most primitive among the Polymorphinidae and is known 



from the Triassic, Jurassic, and Lower Cretaceous of Europe. Provisionally we 



include in the group those forms having the spiral chambers added in planes 



more than 90^ but less than 144° apart from one another. 



b. Chambers added in planes 90° apart from one another, that is, arranged in a 

 tetraloculine series at least in the later stage Quadrulina. 



This group is also known onlj^ from the Jurassic and Lower Cretaceous of 

 Europe. 



c. Chambers added in planes 120° apart from one another, that is, arranged in 

 a spirally triloculine series. Chambers more or less overlapping, giving the test 

 a globular or fusiform appearance. This group should be studied in detail. At 

 present we include the group in Eoguttulina because of its spiral arrangement of 

 chambers. 



d. Test with the early chambers spiral, later ones becoming biserial. 



Paleopolymorphina. 



e. Chambers more or less elongated, added in planes 144° apart from one 

 another, that is, the chambers arranged in a quinqueloculine series. This group 

 is subdivided into two divisions — one, Guttulina s. str. in which each succeeding 

 chamber is removed farther from the base; the other, Sigmoidina, in which 

 normally each succeeding chamber entirely embraces the earlier ones of its series. 



< Mem. Accad. Sci. Istit. Bologna, ser. 5, vol. 8, 1900, p. 35, fie. 39. 



