1 82 NEW YORK STATE MUSEUM 



Globigerina didymi Matthew 



Plate 4, figures 20, 21 a, b 



Globigerina didyma Mitthsw, 1895, Trans. N. Y. Acad. Sci., 

 14:111, pi. I, figs. 7cL, b. (Not Matthew, ibid, v. 12, pi. i, figs, i and 4) 



In addition to typical Globigerina bilobata d'Orbigny 

 foroTisi of two chambers, such as seen on slide i where the segments 

 are SDmewhat smaller and of unequal size, there occur a number 

 of specimens on this same slide where the segments are larger, 

 thicker walled and of nearly equal diameter. Such varieties consti- 

 tute the Globigerina didyma Matthew described from 

 the Cambrian (Middle) of Hanford Brook, N. B. (Div. i band i). 



Matthew's description reads as follows: "Multilocular, probably 

 consisting of four chambers, of which the two final ones are of nearly 

 equal size. There is an arched mouth at the edge of the final 

 chamber, on the opposite side from that whereon the small primary 

 chambers are situated." 



There is not much ground for recognizing such subspecies as 

 Globigerina didyma or Orbulina ovalis from 

 modified forms of Globigerina bilobata, trilobata, 

 and Orbulina universa which have long been established. 

 Matthew is right, however, in separating these modifications, as 

 varietal subspecies of true Globigerinae, from the more complex 

 and highly multichambered G. cretacea and G. bulloides 

 of existing oceans. As cross sections of four-lobed Globigerinae 

 would give forms shown as two lobed, we believe we are right in 

 making a distinction between G. bilobata and G . didyma 

 and feel that these really represent primitive forms of this important 

 genus. 



Genus DISCORBINA Parker & Jones 



The name Discorbina so long used and well established in all 

 foraminiferal literature has recently been replaced by Dr J. A. 

 Cushman and written Discorbis Lamarck. As this does not 

 accord with the termination of the genera among Foraminifera and 

 as Lamarck in the same report used the term Discorbites which 

 later was used for Discorbis, Discorbina and Rosalina, we do not 

 care to adopt this term or spelling. Moreover, the term Discorbis 

 has been used by few students of the Foraminifera ; and the English 

 paleontologists, in papers as late as 191 7, retain the term Discorbina. 



The genus does not seem to be so well represented in early Paleozoic 

 formations as the more highly constructed related genus, Rotalia, 

 which is present in Silurian strata and is well known from the Trias 



