330 NEW YORK STATE MUSEUM 
tinctions on the determinations made by Holm in Eurypterus 
fischeri, this appendage in the female consists of a narrow, convex, 
scalelike, sagittate-based sheath, which appears to be formed by the 
fusion of two nearly equal portions, the anterior overlapping, and pro- 
jecting posteriorly to cover partially a slightly shorter, simple, lance-linear 
appendage in a cleft of the following sternite. In the male the appendage 
is confined to the first sternite, the second being entire. It is proportionally 
shorter and broader, convex and lanceolate with the posterior free end 
slightly produced. Postabdomen composed of six ring segments. The 
first is readily distinguished from the segments of the preabdomen by 
postlateral prolongations. It appears to be formed by the fusion at their 
appressed ends, of a sternal and a tergal portion, the latter of which is 
the longer. The following segments are simple, bandlike rings. Telson 
long, lanceolate, with dorsal carination. Epistoma convex, peltiform, 
dividing in molting or under stress of compression, through the middle, 
joined at the sides to a narrow doublure. Preoral appendages attached 
at the posterior end of the epistoma; short, stout, composed of three joints, 
the two distal a little shorter than the basal, and forming a pair of eden- 
tulous, bevel-edged pincers, which normally are folded back so that their 
tips converge close to the anterior end of the mouth. Endognathites 
increasing in length from the first backward, moderately robust, spiniform, 
composed of seven joints, of which the third to the sixth inclusive bear 
a pair of spines. Swimming arms narrow, lanceolate paddles, composed 
of eight joints and a rudimentary ninth inserted in a notch on the innet 
side of the eighth or palette. The proximal joint, or gnathobase, has the 
form of an upright retort. The seventh bears on the inner half of the 
distal end a subtriangular lobe demarked by a suture. Metastoma elon- 
gate, cordate. 
Type, H. socialis Sarle. 
In the elaborate comparison with other genera which Mr Sarle adds 
to the generic diagnosis, the characters suggesting Pterygotus, as well as 
the resemblances to Eurypterus and Slimonia, are fully discussed. Since 
the date of his study the rocks of New York have afforded representations 
of this interesting genus in the Shawangunk grit and the Frankfort shale. 
These new forms suggest a somewhat different conception of the relation- 
ships of Hughmilleria, which is most conveniently set forth by annotating 
Sarle’s discussion of the relationships of the genus. 
As characters suggesting Pterygotus are cited: The rounded trian- 
‘gular or semielliptic outline of the head as seen in Pt. banksii Salter 
