126 BULLETIN 104, UNITED STATES NATIONAL MUSEUM 



the later development becoming biserial and rapidly enlarging; wall 

 calcareous, coarsely perforate; aperture in the early stages peri- 

 pheral or extending slightly to the dorsal side, in the adult an elongate, 

 open slit at the outer end of the chambers, with a lip. 



This is a genus derived from Cibicides, in which the later develop- 

 ment departs from the close coiled character usual in this family, 

 and becomes definitel}^ biserial. It is found widely distributed in both 

 the Pacific and Atlantic, and is found fossil in the Miocene of Florida 

 and probably elsewhere. 



The genus has many parallelisms in the other groups of the For- 

 aminifera, such as Spiropledammina, Heterohelix, and Spiropledoides, 

 and especially Mooreinella in the Trochamminidae, which has also 

 a trochoid young stage and becomes biserial later. 



DYOCIBICIDES BISERIAUS Cushman and Valentine 



Plate 24, figure 2 



Dyocihicides hiserialis Cushman and Valentine, Contrib. Dept. Geology, 

 Stanford University, vol. 1, No. 1, 1930, p. 31, pi. 10, figs. 1, 2. — Cushman, 

 Bull. 4, Florida Geol. Surv., 1930, p. 62, pi. 12, figs. 6 a, b. 



Truncatulina variabilis H. B. Brady, Parker, and Jones (not d'Orbigny), 

 Trans. Zool. Soc. London, vol. 12, 1888, p. 227, pi. 45, fig. 17. 



Test very much compressed throughout, periphery subacute, the 

 early portion close coiled, trochoid, later chambers becoming biserial; 

 chambers very slightly inflated, distinct, 7 to 8 in the last whorl 

 of the coiled portion; sutures very distinct, on the dorsal side of the 

 coiled portion limbate and flush with the surface, others depressed, 

 not limbate as are all those of the ventral side; wall finely, evenly, 

 and conspicuously perforate, otherwise smooth; aperture nearly 

 peripheral in the early portion, becoming terminal in the biserial 

 portion. 



Measurements of type specimen: Length, 0.90 mm.; breadth, 

 0.60 mm.; thickness, 0.20 mm. 



There is a single specimen in the collections studied which is figured 

 here. It is from Albatross Station D2416, off Georgia in 276 fathoms. 

 Brady, Parker, and Jones had it from the Abrohlos Bank oft' Brazil. 

 The specimen has evidently been worn and smoothed, possibly by 

 the digestive acids of a fish or holothurian. It is identical with the 

 California material and that from the Miocene of the Choctawhatchee 

 marl of Florida. 



Some of the specimens assigned to " Truncatulina variabilis" may be- 

 long here, but it is very different from the type of d'Orbigny's species 

 in the Canaries report. 



