130 
Zygoballus terrestris, Em. 
Attus palustris, Peckham. 
Synemosyna formica, Hentz. An ant-like spider. Common 
on spice bush plants at Indian Reservation in 1900. 
Synageles picata, Hentz. An ant-like spider which frequent- 
ly thrusts forward its second pair of legs and moves them about 
as an ant does its antennae. 
NOTES ON SOME ERUPTIVE DIKES NEAR ITHACA. 
Puitie F. SCHNEIDER. 
SEPTEMBER IQ, 1902. 
The upper end of Cayuga Lake lies in a depression several 
hundred feet below the surrounding surface, so that the streams 
which flow into it have produced deep gorges with excellent expo- 
sures of the Hamilton, Tully, Genesee, and Ithaca formations. 
In several of these gorges narrow dikes of igneous rock 
occur and it is probable that a careful examination of all would 
furnish numerous additional exposures to the list given below. 
These dikes were first mentioned by Vanuxem, in the Report 
of the Third District of New York, page 169. He says: “ Near 
the Tully limestone in the fissures of the slaté (Genesee) are two 
narrow veins of semi-crystalline rock of a blackish-brown color, 
becoming olive by alteration. It appears to be a mixture chiefly 
of serpentine and limestone having the appearance of a Trap rock. 
There are also two similar sets of veins near the foot of the sec- 
ond falls, in the same ravine. Both sets of veins traverse the 
creek at nearly right angles to its course.” 
They are again mentioned by Dr. J. F. Kemp in a paper en- 
titled, “* Peridotite Dikes in the Portage Sandstones, near Ithaca, 
N. Y.” in the American Journal of Science, November, 1891, 
page 410. He quotes Vanuxem and adds that he “ had recently 
visited the locality but only the two dikes near the upper falls of 
Vanuxem could be found. They are each about one inch wide 
and only show over a short space as they disappear above and 
below. They were inaccessible and from the distance of a few 
