(66 NEW YORK STATE MUSEUM 
other authors taken up this problem as far as we are aware. In 
several species we have found distinct openings in the corners where 
the posterior points of the triangular areas of the opercular plates 
meet the lateral points of the hastate basal portion in the unpaired 
lobe of the female genital appendage. These lateral points are as a rule 
extended into earlike or scroll-lke lobes that cover the openings. Since the 
paired interior tubular appendages observed in Eurypterus end at these 
lateral points, it 1s certain that they emptied here, as suggested by Holm, 
who considers them as auxiliary generative organs. | 
The large opercular appendage of the female is but a median tongue 
and not a tube, and it is probable that it concealed the complicated 
terminal portions of the genital organs, as the median part of the operculum 
still does today in the arachnids Phrynus and. Thelyphonus. Gas- 
kell [p. 192] has drawn a restoration, representing these genital organs 
“in accordance with our knowledge of the nature of these organs in the 
present-day scorpions, as a median elongated uterus, bilaterally formed, 
from which the genital ducts passed, probably as in Limulus, towards a 
mass of generative glands in the cephalic region, and not as in Scorpio or 
Thelyphonus, tailwards to the abdominal region.’”’ We surmise that the 
female eurypterid thrust this chitinous opercular appendage, together 
with the opercular plate, into the sand during oviposition, just as Limulus 
does today. 
| It is possible that the paired tubular organs mentioned above are not 
auxiliary generative organs, as surmised by Holm, but are the genital ducts 
and that the openings observed by the writers are the apertures of these 
ducts leading into the median uterus. 
The sternal plates of the third to the sixth mesosomatic somites are 
well developed, forming the four sternztes following the operculum. These 
plates are always slightly arched forward, the anterior margin being slightly 
convex, the posterior concave. The antelateral angles are produced 
into rounded lobes and the median line is marked by a suture, along which 
they readily separated. The sternites were often more arched than the 
