8 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 134 
Family TROCHAMMINIDAE Schwager, 1877 
Genus TROCHAMMINA Parker and Jones, 1859 
TROCHAMMINA LAEVIGATA Cushman and Bronnimann 
PLATE 3, FIGURE 3 
Trochammina laevigata CUSHMAN and BroNNIMANN, Contr. Cushman Lab. 
Foram. Res., vol. 24, pt. 2, p. 41, pl. 7, figs. 21, 22, 1948. 
Diagnosis—Shape of test: Trochospiral, with a round, slightly 
lobate equatorial periphery ; dorsal side slightly convex or almost flat, 
ventral side concave owing to the presence of a small, deep umbilicus ; 
axial periphery rounded. In large specimens, with highly inflated last 
chambers, the dorsal side may be very slightly concave. Wall: Mi- 
nute sand grains set in a fine cement; surface smooth, somewhat pol- 
ished. Color reddish brown to fawn. The protoconch and first whorl 
are dark brown; the wall of this early portion of the test is apparently 
composed of a chitinous layer with no adherent agglutinated material. 
Being extremely fragile, the early chambers have often been exca- 
vated. Chambers: Inflated ventrally, less strongly dorsally. Seven- 
teen to twenty chambers arranged in about three whorls with five to 
six chambers in the last whorl. The rate of increase in size of the 
chambers in the last whorl varies, some specimens having relatively 
larger, more inflated, final chambers than others. Sutures: Distinct, 
almost flush with surface dorsally, depressed ventrally. Straight or 
slightly curved. Aperture: An interiomarginal slit on the ventral 
side of the last chamber extending from the umbilicus one-third to 
one-half the distance to the periphery ; a narrow, prominent lip is seen 
in well-preserved specimens. Size: Maximum diameter of figured 
hypotype 0.48 mm., thickness of hypotype 0.21 mm. 
Range for species -—Diameter approximately 0.3 mm, to approxi- 
mately 0.8 mm. Thickness approximately 0.15 mm. to approximately 
0.37 mm. 
Locality.—Figured hypotype (U.S.N.M. No. P5106) from sample 
J.S. 273, Carenage Swamp, west coast of Trinidad, B.W.I. 
Distribution—Trochammina laevigata Cushman and Bronnimann 
is widespread in all inshore, brackish-water areas of Trinidad. 
Remarks—This species is very close to Trochammina inflata 
(Montagu). Montagu’s original figure and description of Nautilus 
inflatus (Montagu, 1808, p. 81, pl. 18, fig. 3) are too poor to be used 
for comparison. Brady’s description and figures of Trochammina 
inflata (Montagu) (Brady, 1884, p. 338, pl. 41, figs. 4a-c), shows ex- 
tremely slight differences between this species and Trochammina 
