FOBAMINIFEKA OF THE NORTH PACIFIC OCEAN. 19 



SPH-SROIDINA DEHISCENS Parker and Jones. 

 Plate 10, fig. 2; plate 13, fig. 1. 



Sphxroidina dehiscens Parker and Jones, Philos. Trans., vol. 155, 1865, p. 369, 

 pi. 19, fig. 5, a, &.— H. B. Brady, Quart. Journ. Micr. Sci., vol. 19, 1879, 

 p. 295; Rep. Voy. Challenger, Zoology, vol. 9, 1884, p. 621, pi. 84, figs. 8-11.— 

 Egger, Abh. kon. bay. Akad. Wiss. Mxinchen, CI. ir, vol. 18, 1893, p. 376. 

 pi. 13, figs. 58, 59.— Goes, Bull. Mus. Comp. Zo5l., vol. 29, 1896, p. 67.— 

 Flint, Rep. U. S. Nat. Mus., 1897 (1899), p. 325, pi. 71, fig. 2.— Bagg, Proc. 

 U. S. Nat. Mus., vol. 34, 1908, p. 155. 



Globigerina seminulina Schwager, Novara Exped., Geol. Theil, vol. 2, 1866, p. 

 256, pi. 7, fig. 112. 



Description. — Test subglobular, composed of a few chambers ar- 

 ranged as in S. bulloides but distinguished even in early stages by 

 the large perforations and translucent test; chambers in later develop- 

 ment separated by deep fissure-like sutures, often in adult specimens 

 nearly closed by the fimbriated edges of the chamber; wall thick, con- 

 spicuously perforate, somewhat reticulate, rough; aperture an arched 

 opening into the chamber from the deep fissure near its base. 



Diameter up to 1.5 mm. 



Distribution.— Brady records this species from four Challenger sta- 

 tions in the North Pacific, depths ranging from 500 to 2,100 fathoms. 

 Picaglia records it from two North Pacific stations of the Vettor Pisani . 

 Goes records it from two Albatross stations in the western Pacific, 

 D 3371 in 770 fathoms and D 3400 in 1,322 fathoms. Bagg records 

 it from a number of Albatross stations near the Hawaiian Islands at 

 depths ranging from 305 to 1,544 fathoms. I have found specimens 

 from a great number of stations in all parts of the North Pacific 

 where Globigerina ooze material has been available. In depth these 

 range from 323 to 2,175 fathoms. Often the specimens have been 

 abundant and excellent for showing the developmental stages. 



In the young of S. dehiscens the test is comparatively smooth but is 

 conspicuously perforate with comparatively large pores. At this time 

 there is almost no trace of the deep sutures and except for the pores 

 and the translucent test the resemblance to a specimen of S. bulloides 

 is close. As chambers are added usually a triangular area is left, at 

 first very small and inconspicuous, later becoming more marked, similar 

 to the specimen figured by Schwager noted above. By degrees as 

 chambers are added the sutures become wider and finally in adult 

 specimens they are at the bottom of deep fissures which are wide 

 open, but which in old-age specimens are partially closed near the 

 exterior by the growing in of the side walls near the surface. In 

 such specimens the walls at the edge of these fissures are often con- 

 siderably raised and fimbriate and the remainder of the wall becomes 

 rough and somewhat reticulate. In the old-age specimens the wall 

 is very thick and the pores are conspicuous in section. 



