63 
trilobites are not confined to a geological period 
more remote than that which has produced the ani- 
mals with oculiferous tubercles. 
Genus Ocyrera. Brongniart. 
In the vast quarries of slate at Angers, in France, 
there is frequently noticed two very remarkable or- 
ganic remains, which have for a long time excited the 
attention of naturalists. To receive these curious 
relics, Professor Brongniart established the genus, 
Ogygia, which he thus characterizes. Body much 
depressed—elongated into an ellipse, terminated in 
points—nearly equal at its extremities, and not capa- 
ble of contracting itself into a spherical form. The 
buckler is bordered by a slight longitudinal furrow, 
rising from its anterior extremity, and its posterior 
angles terminating in elongated points.. The abdo- 
men has eight articulations, and its longitudinal lobes 
are not very prominent. The eyes are neither promi- 
nent nor reticulated and there are no other protube- 
rances on the buckler. | 
In Professor Brongniart’s original work on the Tri. 
lobites, he has described the two specimens from 
Angers, under the specific names of Guettardi, and 
Desmarestil, in compliment to M. M. Guettard and 
Desmarest; and in De La Beche’s Manual of Geolo- 
sy, we are informed that he has since identified two 
other species; one of which is supposed to be found 
“in North Americas; this he calls Ogygia Sillimani; 
the banks of the Mohawk River, near Schenectady, 
