8 Trans. Acad. Sci. of St. Louis 
posterior-median area, with no trace externally of a 
separating groove or concavity. 
Internally, a small, square hinge-plate in the left valve. 
The blade two-thirds of the length of the entire shell, 
thin, broad dorsally, the middle and ventral portions 
narrower, its entire length reflected slightly posteriorly. 
The ventral knob narrow, long, its base extending dor- 
sally for a considerable distance. The juncture of the 
anterior with the anterior-median area marked by a nar- 
row, thickened chord. The juncture of the auricle with 
the posterior-median area hardly visible. 
Pallets (fig. 10) with long, stout, opaque white stalks. 
The blade short, broad, investing a considerable por- 
tion of the upper part of the stalk in a thin sheath. The 
outer face convex. The proximal third of the blade eal- 
eareous, arising from the stalk in an abrupt curve. The 
middle third swollen, covered with a light horn-colored 
periostracum. The distal third covered with a dark 
chestnut colored periostracum with a deep central sinus 
dividing this portion of the blade into two shallow cups, 
the outer face considerably more deeply indented than 
the inner. The inner face of the blade flat, its distal two- 
thirds covered with a periostracum irregularly streaked 
with narrow bands of light and dark chestnut. 
The posterior end of the tube with a long delicate 
partition (fig. 11) dividing the tube into equal parts. 
The type (Mus. Comp. Zo6l., 45306) is from Guan- 
tanamo, Cuba. 
The measurements of the type are: 
Shell, height 4.5 mm.; length 4.5 mm. 
Pallets, total length 4.3 mm.; length of stalk 3 mm.;. 
width of blade 1.6 mm. 
The shell of this species is very closely related to that 
of Teredo clapy Bartsch (Proc. Biol. Soc. Washington, 
