NO. 3563 EUPHILOMEDES AROSTRATA—KORNICKER th 
have scalloped outline formed by crescent-like marginal denticulations. 
Shell surface with irregular polygons and normal pore canals (fig. 6p). 
Polygons having pore canals are smaller than average. Distribution 
of pore canals differs in males and females; males have fewer large 
canals through which large hairs pass and more small canals containing 
minute hairs. Large hyaline polygons interpreted as areas of muscle 
attachment on the female valve, less distinct on male valve. Oval 
hyaline area with polygon border distinct, located dorsal to hyaline 
polygons. Hinge elements of male identical to those of female (fig. 7). 
Inner lamella broad with vestibule as in female, but narrower along 
ventral margin. Radial canals not observed in male. Line of con- 
crescence not identified with certainty on male, but may lie just 
within inner margin of selvage. I{ so, marginal zone of male is much 
narrower than that of female. Selvage of male similar to that of 
female. List as well as striations on anteroventral part of inner 
lamella not observed on male. 
Distribution of hairs differs on male and female: Hairs that flare 
distally and have concave tips less abundant than on female, restricted 
to anterior one-third of valve surface and to ventral margin (fig. 6c); 
minute tapered hairs apparently more abundant, more or less evenly 
distributed over valve surface. Long tapered hairs more abundant 
on posterior one-third, especially along posterior margin; also present 
along ventral and anterodorsal margins interspersed with flaring 
hairs. Single tapered hair located behind posterior hinge elements 
of left and right valves on both male and female. Normal pore 
canals from which hairs protrude located in polygons smaller than 
surrounding polygons. Polygons containing flared hairs generally 
bordered by five polygons; polygons with long tapered hairs by six 
polygons; polygons containing minute tapered hairs by only four 
polygons. Pore canals containing minute tapered hairs apparently 
smaller in diameter than pore canals with long tapered or flared hairs. 
Ten long hairs on left valve and nine on right form row on inner 
lamella behind rostrum; not bifurcate like hairs similarly located on 
female shell (figs. 5r, G). Small bare hair located below rostral sinus 
in same position as on female. Row of 19 bare hairs on right valve 
and 21 on left on anterior part of ventral inner lamella; not brushlike 
as are similarly located hairs on female (figs. 5a, 3). About 32 short, 
tapered hairs, more or less in two rows, on inner lamella extending 
from its posteroventral part to posterior hinge element (fig. 5x). 
Dimensions.—Length 1.00 mm., height 0.60 mm. 
First antenna (fig. 8a): First joint without bristles; second joint 
with transverse rows of hairs along ventral margin and three bare 
bristles; third joint with one bare bristle on ventral margin and two 
bristles on dorsal margin; of these the shorter is bare, the longer has 
