848 
Fig. 
DR. G. J. HINDE ON RECEPTACULITIDA. 
la. Another specimen from the same locality, also imperfect, showing 
the interior surface. The vertical and transverse ribs are formed by 
the horizontal spicular rays, which are now partially amalgamated 
together. Natural size. 
14. A portion of the outer surface of the typical example of the genus, 
now in the Jermyn-Street Museum, showing the slightly elevated 
knob in the centre of each of the spicular summit-plates. Natural 
size. 
lc. A portion of the inner surface of a fragmentary specimen, enlarged 
three times, showing clearly the horizontal rays and the indepen- 
dence of the spicules. 
Figures 2, 2a-e. Acanthochonia Barrandei, Hinde. 
2. Two nearly entire individuals and portions of two others, partially 
imbedded in a fractured piece of rock. The bases and outer surface 
of the specimens are shown. Natural size. These and the following 
examples are from Silurian strata, Etage E. of Barrande, at Bubo- 
witz, near Prague. They were obtained for the British Natural 
History Museum from Barrande himself. 
2a. The basal portion of an individual, enlarged three times, showing 
the eight spicular plates forming the nucleus, and the disposition of 
the summit-plates succeeding them. 
26. A portion of the outer surface of another specimen, enlarged three 
times, showing the arrangement of the spicular summit-plates, from 
the nucleus, at the apex of the figure, to nearly halfway to the 
margin of the cup. In the centre of the figure are shown the two 
modified spicular plates, one pentagonal and the other triangular, 
which are developed at the intercalation of a fresh row of spicules. 
2¢. A portion of the outer surface of a specimen in which the summit- 
plates are partially destroyed, showing the horizontal spicular rays 
beneath. Enlarged three times. 
d. A vertical section of two specimens imbedded in the rocky matrix. 
Natural size. 
2e. A vertical section, passing nearly through the centre of a specimen, 
enlarged three times, showing the extension and the free termination 
of the vertical rays of the spicules. The spicular plates and the 
horizontal spicular rays are undistinguishably merged together in a 
thick outer layer of crystalline calcite (shown white in the figure), 
and the free vertical rays are now of the same material. 
bo 
Figures 3, 3a-m. Receptaculites occidentalis, Salter. 
3, 3a, 3. Different views of a fragment of a platter-shaped specimen, 
partially freed by acid from the calcitic matrix. Natural size. 
3. Shows the perforated inner or upper layer. 
3a. The spicules connected with the inner layer. 
36, The summit-plates of the spicules of the outer or under surface. 
Collected by the author from the lower beds of the Trenton lime- 
stone at Pauquettes Rapids, Ottawa River, Canada. 
3¢-g. Different views of fragments of the inner or upper layer. 
3c. The upper or exposed surface. Natural size. 
3d, e. The same surface, enlarged three times, showing its rough chan- 
nelled character. 
3f, g. The reverse or inner side of the same fragments. -The smaller cir- 
cular or elliptical apertures are the canals which extend through the 
inner layer, and the larger shaded circles in figs. 3f, g show the 
places of attachment of the vertical spicular rays to the inner surface 
of the layer; in some places the broken ends of the rays yet remain. 
ee 
