JOURNAL 
OF THE 
ACADEMY OF NATURAL SCIENCES 
OF P H I L A D E P H I A. 
URAATELLA GRACILIS, A FRESH -WATER POLYZOAN. 
By Prof. Jo.sefii Leidy. 
Upwards of thirty years ago, and on several snhsequent occasions, in the Pr«Kre<liiigs 
of this Acadeniv (1851, 321; 1854, 191; 1858, 1; and 1870, 100), the writer has 
briefly described or noticed an interesting fresh-water ciliated polyj., or pol>/<Nm, to 
which the name of Urnatella gracilis was given. It was first chscovenal in the 
Schuylkill River, under low-tide mark, below Fairmount dam, Philadelphia. It was 
found in association with PhmateJla, PalndiceVa. and other animals common m such 
positions. At the times of collecting it in 1854 and in 1870, it was in comparative 
abundance in the locality, but lately appears to have become scarce, due to the 
destnretive influence of the city scAvage which now flows ,so abundantly into the river 
In similar places under flrvorablc circumstances, Urnntdhi is probably not ran-, though 
incidentallv in the search of aquatic animals 1 have not found it elsi-when-. nor liaAc 
of the drawings accompanying the present coramunication weie m. 1 Schuylkill 
at the mouth of the neighboring canal. In the autumn of 18 . 6 , ^ „r 
River, below the city, by dredging, and I had the agreeable '‘"t'cip expectations for we hmiid Oie 
together with other interesting animals. We were isapponi imbued with oil, derive*! from 
sediment of the river, everywhere from the city to the mouth o the Schuylk U, imbued 
the waste of the gas-works and oil refineries, so that no living thing could exist. 
2 .JOUR. A. N. S. PHILA.,VOb. IX. 
