REPORT OF THE DIRECTOR I918 183 



on. The segments are often very highly curved or arched, the 

 walls thin and the periphery sharp. We identify one species which 

 seems to belong here. 



Discorbina orbicularis (Terquem) 



Plate 5, figures 6, 70, 6 

 Rosalina orbicularis Terquem, 1876, Anim. Plage de Dunkerque, 



p. 75, pi. ix, fig. 4, a, b 

 Discorbina orbicularis Parker & Jones, 1 896, Paleont. Soc. , 



50:295, pi. vii, fig. 31, a-c 

 Discorbina orbicularis Vadasz, 1910, Triasforam. aus dem Bak- 



ony, p. 31, pi. 2, fig. 4 (Called D. orbicularis d'Orbigny sp. instead of 



Terquem) 

 Discorbina orbicularis Jones, 1896, Pal. Soc, 50:295, pi. vii, 



fig. 31, a-c 



This species must not be confused with the Rotalia orbi- 

 cularis d'Orbigny, probably the form described originally by 

 d'Orbigny in 1826 as Discorbis orbicularis, and also 

 Gyroidina, as this is a true double-walled septal type such as 

 the Rotalia of today's literature. We follow Brady in this nomen- 

 clature, both genera and both species with which we are concerned 

 being discussed and described by him in his Challenger mcnograph. 

 This type according to Brady is best developed today off coral 

 reefs but is known from the North Atlantic as well as in southern 

 waters off the coast of Australia. It has been recognized in off-shore 

 deposits down to 435 fathoms. 



In our type there are but four chambers in the final whorl, highly 

 arched and obliquely set; and there are three volutions altogether 

 comprising between fourteen and sixteen segments with the central 

 chamber slightly eccentric. The type is best shown on slide 6 

 and measures 0.14 mm in diameter. The outer disc is not circular, 

 as the final segment overlaps unsymmetrically and the segments 

 expand and become wider on their outer margin. We think that 

 some of the transverse sections may belong to this type, but mcst 

 of such we identify are Pulvinulinae. 



The species has been reported in the Trias of Bakony, in the 

 Neocomian of Surrey, England, and in various Tertiary deposits. 



Genus TRUNCATULINA d'Orbigny 



Of all rotaline forms present in the Bonaventure cherts, the 

 genus Truncatulina is the most abundant. At least three distinct 

 species occur and there are many of these present. Fortunately 



