THE EURYPTERIDA OF NEW YORK 63 
line. The distal end is produced into two short pointed pieces. The 
second single piece underlies or is telescopically pushed into the first and 
is of the same or very similar form as the first. Connected with the female 
genital apparatus were paired internal tubular appendages first correctly 
recognized in E. fischeri. These are also well seen in specimens of 
EK. remipes [pl. 8, fig. 1Jand E. lacustris [pl.12,fig. 2]. Inone 
of the representatives of the latter species [Buffalo Society of Natural 
Sciences] both tubes lie to one side of the median lobe [see text fig. 20] 
thereby indicating that they extended free into the interior of the body. 
In the male the two lateral opercular plates are more regularly rect- 
angular in outline and come into contact along the median line. The 
genital appendage is very small and composed only of two single pieces. 
No pentagonal areas are set off by sutures. The principal single appendage 
consists of a median piece with parallel sides exposed to the outside and 
two larger wings underlying the opercular plates; the second appendage is 
very small, triangular and adjoins the first. 
In other genera, as Hughmulleria and Pterygotus, the genital appen- 
dages are clearly much simpler. In Hughmiulleria only one sagittate-based 
lobe is found on the female operculum [pl: 62, fig. 9, ro] and in the male 
a convex, broadly lanceolate lobe [pl. 62, fig. 11]. 
In Pterygotus these sexual appendages are not yet clearly dis- 
tinguished, but they seem to be little advanced beyond those of 
Hughmilleria. The female appendage in its simplest form [P.bilobus, 
see Woodward, 1869, p. 61, pl. 12, fig. 1c; Laurie, 1893, pl. 2, fig. 14] is a 
straight, narrow, very slightly expanding plate with a ridge down the 
middle and ending in a bluntly triangular point, while, where more highly 
developed, as in P. osiliensis, it possesses a rhombic sagittate 
base, connected by sutures with the lateral opercular plates, and con- 
tinued into the free club-shaped principal part with rounded extremity. 
In some cases, as in P. anglicus, [see Huxley and Salter, 
pl. 3] and in an unidentifed form from Otisville [pl. 78, fig. 3] the 
extremity was expanded into a disklike body, the whole appendage 
