44 BULLETIN" 161, UNITED STATES NATIONAL MUSEUM 



broader in the last-formed chamber. Length, up to 0.55 mm.; diam- 

 eter, 0.25 mm. 



The types are from 7 fathoms off Rotonga. 



This is apparently a species of shallow warm water and has a wide 

 distribution as the following records of our material show: In the 

 vicinity of the Fiji Islands, 12 and 24 fathoms off Nairai; 12 fathoms 

 off Levuka; 3 fathoms, Viva Anchorage; and 40-50 fathoms off Fiji; 

 as well as at Mokaujar Anchorage. Specimens also were found com- 

 mon at Vavau Anchorage, Tonga Islands, in 18 fathoms, and rare 

 specmiens occurred in the material from Rongelap Atoll, Marshall 

 Islands. 



TRIMOSINA PERFORATA Cushman 



Plate 12, Figure 6 



Trimosina perforata Cushman, Journ. Washington Acad. Sci., vol. 19, p. 157, 

 figs, la, h (in text), 1929. 



Test small, generally triangular in both side and end views, angles 

 acute; chambers triserial throughout, rapidly increasing in size as 

 added, the angles of the chambers usually protruding and early cham- 

 bers sometimes twisted; sutures distinct, not depressed, slightly lim- 

 bate; wall calcareous, finely perforate with coarser perforations along 

 the borders near the sutures connecting with the interior by definite 

 tubules, generally smooth, thin and nearly transparent ; apertural face 

 convex, with numerous ridges and irregular projections, aperture 

 consisting of a long narrow opening connecting with the basal mar- 

 gin by a narrow slit at a sharp angle to the axis of the main opening, 

 bordered by a distinct thickened lip, the apertural face with numerous 

 irregularly rounded openings. Length, 0.50 mm.; breadth, 0.35 mm. 



This species, which was described from 40-50 fathoms off Fiji, 

 seems to be a very limited one in its distribution; it has not been 

 recorded elsewhere, although it is fairly common at the type locality. 



TRIMOSINA SIMPLEX Cushman 



Plate 12, Figure 7 



Trimosina simplex Cushman, Journ. Washington Acad. Sci., vol. 19, p. 158, figs. 

 2o, h (in text), 1929. 



Test of medium size, triangular in both side and end views, angles 

 acute; chambers triserial throughout, uniformly increasing in size as 

 added, angles of the chambers slightly spinose, the outer angle thick- 

 ened, almost carinate; sutures distinct, not depressed, very slightly 

 limbate, rather evenly curved; wall calcareous, coarsely perforate, 

 especially along the borders, smooth, fairly thick but translucent; 

 apertural face slightly convex, fairly smooth, the aperture elongate 

 without a lip, and with a few supplementary openings in the center of 

 the terminal face. Length, up to 1.00 mm.; breadth 0.50 mm. 



