246 E. A. ANDREWS 
somite they are in contact at the median line of the abdomen. 
The elliptical transversely elongated stumps of the first append- 
ages are 5 mm. long and those of the second about 3 mm. 
Commonly these appendages are carried forward horizontally 
under the thorax between the thoracic legs in a deep depression 
of the thoracic sterna. The first pair lie close side by side with 
their median faces in contact. The second pair lie over and largely 
conceal the first, since their form enables them to come to the 
middle of the body beneath the first pair in spite of the fact that 
their bases are attached to the sterna, so far from the middle line. 
In a dead male one may move the appendages upon their at- 
tached bases as follows: 
The first may be moved upon its base from the horizontal up 
toward the vertical only about 45°. The membrane on the anter- 
ior face of the joint at the base of the appendage is stretched to 
its limit when the appendage is pulled up a little beyond sixty 
degrees, so that this appendage is never vertical and cannot swing 
back and forth through a wide arc as do the ordinary swimmerets. 
The distance traversed by its tip issome twoem. The appendage 
may also be rotated a very little at its base and moved from side 
to side a little so that ts tip travels some 5 or 6 mm. 
The apex of the second may be drawn from the horizontal up 
a little beyond the vertical; but neither the basal protopodite 
nor the endopodite travels more than 90°. They are set together 
at a large angle, so that while the main length of the appendage is 
horizontal the basal part never is, and when the base goes back 
some 90 degrees the horizontal part is swung past the vertical 
line. The tip traverses some 38cm. The base may be rotated 
a little and moved from side to side so that the apex travels 6 or 
7 mm. 
STRUCTURE AND ANATOMY OF THE FIRST STYLET 
The first abdominal appendage of the male is a very stiff cal- 
cified mass of the general shape of an awl, some 17 mm. long, but 
having two tips. There is a groove along more than half its length 
and the base is articulated to the ventral shell of the anima’ so 
