REPORT OF THE DIRECTOR I918 173 



form showing two segments only, but which we doubtfully place 

 under this species. It is not at all typical, but the specimen seems 

 to be perfect and complete and much less involute than the 

 C . g i b b a which we also identify in these cherts. A better speci- 

 men, shown on slide 5 (X) has four chambers. 



Cristellaria gibba d'Orbigny 



Plate 3, figures 22, 24 



Cristellaria g i b b a d'Orbigny, 1839, Foram. Cuba, p. 63, pi. vii, 



figs. 20, 21 

 Cristellaria pulchella Reuss, 1862, Sitz. Akad. Wiss. Wien, 46: 71, 



pi. viii, fig. I 



What appears to be Cristellaria gibba occurs on slide 4, 

 but, unfortunately for absolute identification, the external anterior 

 margin of the ultimate chamber is broken away by a fissure occurring 

 in the chert, so that it is impossible to ascertain whether the aperture 

 is cristellarian or not. The segmentation is identical with the few 

 rapidly enlarging chambers of C . gibba, but there is a slightly 

 more involute structure than the type calls for. There are, however, 

 rather wide variations in this species, near which must be placed 

 C . n u d a Reuss, C . p o 1 i t a Reuss, Robulina concinna 

 Reuss and many other intermediate forms between Cristel- 

 laria crepidula, with its thin complanate test, and the 

 lenticular involute Cristellaria rotulata (Lamarck) . The 

 identification rests upon the outline, arched segments, five shown 

 on the slide, and their rapid expansion upward. If, however, the 

 aperture is central the form is not Cristellaria but Pulvinulina, 

 near P. hauerii (d'Orbigny) ; but the faint marking near the 

 periphery at the third septal line is very like Cristellaria. 



C . gibba has been identified from the Trias and every succeed- 

 ing horizon; but it is best known as a Cretaceous and Tertiary form, 

 and is still found in the North and South Atlantic oceans at depths 

 of less than 500 fathoms. 



Genus POLYMORPHINA d'Orbigny 



But few specimens of the undoubted Polymorphina character 

 appear in the Bonaventure chert. The genus is a particularly 

 difficult one to identify or to determine specifically, as cross sections 

 of segments, often without the aperture position, do not enable 

 one to judge under what type a given specimen belongs. The forms 

 we find are mostly of very minute size; but one rather large form 



