of Hippothoa and Alecto. 125 
James, from which it is distinguished mainly by its more 
slender habit and graceful form, and by its generally having 
its cells arranged in a double or single series. Also, I have 
not hitherto been able to make out in the texture of A. aulo- 
poroides the minute pores which seem to be present in all 
perfect examples of A. frondosa. 
Locality and Formation—Cincinnati Group, Cincinnati, 
Ohio. ‘The species is a common one, and is found upon 
Strophomena alternata, Conrad, and Streptelasma corniculum, 
Hall. 
3. Alecto frondosa, James. Pl. XI. figs. 3-3 d. 
Aulopora frondosa, James. Named, but not figured or described, in 
the ‘Catalogue of the Lower Silurian Fossils of the Cincinnati 
Group,’ 1871. 
Polyzoary creeping, adnate, of reticulating and anastomosing 
branches, which usually become more or less completely con- 
fluent so as to give rise to a thin expanded crust, or which are 
partially reticulated and partially confluent. When the branches 
form a network, the size of the meshes, as well as their disposi- 
tion, is exceedingly variable; but they are usually more or 
less oval, with a long diameter of half a line to a line or more, 
the interspaces between them varying from half a line to two 
lines. The cells are uniserial on the narrowest branches, but 
biserial, triserial, or multiserial on other parts of the coencecium ; 
elongated and tubular, immersed below, but free towards their 
apertures, the terminal portion of the tube being more or less 
elevated above the general surface. Cells from six to eight 
in the space of one line. Cell-mouths terminal, circular, of 
the same diameter as the tube. Entire surface, in well pre- 
served specimens, minutely porous. 
There does not appear to be any reason for doubting that 
this is a true Alecto. It is nearly allied to A. auloporotdes, 
especially as regards the form of the cells; but the greater 
width of the branches and their common coalescence into ex- 
anded crusts, together with the greater number of the rows 
of cells over most portions of the coencecium, communicate to 
the fossil quite a peculiar appearance, and appear to be cha- 
racters of specific value. Since my original description of 
this species, founded on type specimens furnished me by Mr. 
James, was written (in the Report on the Fossil Corals, 
Polyzoa, and Sponges of the State of Ohio, now in course 
of publication), I have examined a large suite of specimens 
which I collected myself at Cincinnati. These enable me to 
assert that, in all well-preserved examples, the entire surface of 
the polyzoary is covered with the apertures of exceedingly 
