338 NEW YORK STATE MUSEUM 
inner spine of each pair is the longer, and the length increases for each 
successive set, from the third to the fifth joints; the spines on the sixth are 
short. The coxal joints are elongate, shghtly curved, widest at the base 
and equal in length to the succeeding two joints. They increase in length 
with each successive pair, and bear on the inner end a series of 15 or 
more, sharp, curved teeth, which decrease in size from the front. On 
each of the fourth coxal joints is a large perforation of the upper side near 
the fixed end. No epicoxite has yet been observed. The second joint 
of the endognathite is divided by constrictions into three transverse 
sections. It is articulated at the fixed end of the coxal joint and is 
fully two thirds as wide. 
~The limbs of the sixth pair are narrow and paddlelike, and consist 
of eight joints and a rudimentary ninth or claw, the seventh and eighth 
forming a shghtly expanded blade. The seventh carries a large, sub- 
triangular, lobelike plate, nearly one half as long as the joint proper, marked 
off from the inner, distalend bya suture. The eighth, or palette, is elongate 
oval with the margin finely incised, and carries the minute claw inserted 
in a notch on the inner side near the tip. On the dorsal surface of the 
seventh and eighth joints, at the proximal end and outer edge of each, 
is a group of minute, craterlike tumescences, which were probably recep- 
tacles for the bases of hairlike bristles. In a swimming arm 29.5 mm 
long, exclusive of the gnathobase, the narrowest joint or the fourth, 
measures 5 mm across; from this point the arm gradually enlarges to 6. 8 
mm on the seventh and eighth joints. When the swimming arms are 
turned back, they reach the line of the fourth or fifth dorsal segment. 
The gnathobases have the form of an upright retort. The inner ex- 
tremity of each is provided with from 18 to 20 sharp, slightly curved teeth, 
which become finer posteriorly. A gnathobase, accompanying a cephalo- 
thoracic shield 22 mm. long, is 16 mm long; the width of the narrow 
necklike portion 6 mm; the width at the base 13 mm. 
The metastoma is longate cordate, the greatest breadth coming 
anterior to the middle.’ The smaller, or posterior end, is truncated and 
has rounded corners. The anterior notch is rather deep and broad. A 
comparison of the length to the greatest breadth of several metastomas 
gives the proportion of 2:1. In an individual having a cephalothorax 
23 mm long the metastoma is 16 mm long. 
The genital appendage differs noticeably in the two sexes. In the 
female it consists of two parts, one carried by the operculum, the other 
by the second sternite. The opercular appendage is a slender, sagittate- 
based, convex, scalelike sheath projecting for about one fifth its length 
beyond the posterior edge of the operculum and appearing to be formed 
by the fusion of two parts. The anterior of these includes the sagittate 
base and a narrower, more convex portion with a flattened border on 
