PROTOZOA. 
291 
ISCHADITES, Murchison. 1839. 
ISCHADITES SQUAMIFER. 
PLATM XXIV, FIGS. 1, 2. 
Dictyocrinites, Conrad. Ann. Rept. Geol. Survey, N. Y. 1841. 
Dictyocrinus squamifer, Hall. Pal. N. Y. Vol. iii, p. 135, p. 7a, figs. 11-13. 1859. 
Receptaculites “ “ Report of State Geologist for 1882. Expl. pi. 23, figs. 1, 2. 1883. 
Body pyriform, regularly rounded on the base, conical above and perforate at 
the summit by an aperture about 5 mm. in diameter. The summit plates of 
the spicules have curved edges and appear to imbricate, the lower sides being 
depressed below the anterior edges of the adjacent inferior plates. In the 
zonal region the plates have a width of from 1 to 2 mm., and their size 
decreases very gradually towards the base and quite rapidly towards the 
summit, where they have a width of less than 1 mm. The vertical spicular 
rays were very slender, having a thickness of about 5 mm. from their distal 
extremities. The original specimen figured by Mr. Conrad has a height of 
34 mm., and a diameter of 33 mm. at the lower third of the height. 
Specimens of this species are quite uncommon and so far as observed they 
are usually completely filled with chalcedony. The type specimen, however, 
is filled with calc spar. 
Formation and locality. In the limestones of the Lower Helderberg group at 
Schoharie, N. Y. 
ISCHADITES BURSIFORMIS. 
PLATE XXIV, FIGS. 12-14. 
Receptaculites bursiformis, Hall. Report of State Geologist for 1882. Expl. pi. 23, figs. 12-14. 1883. 
The original form of this sponge is not clearly shown in the specimens at hand 
on account of the various degrees and directions of compression to which 
they have been subjected. Three specimens are sub-pyriform with terminal 
summits, and two are discoidal with eccentric summits. The zonal plates 
have a width of about 2.5 mm. Near the summit they are small and very 
numerous, and have a width of about 1 mm. None of the specimens show 
