DR. G. J. HINDE ON RECEPTACULITIDA. 833 
tures are of such a character as to render it doubtful whether the 
genus should be ranked under Hexactinellids or Lithistids ; i As- 
treospongia, F. Rom., the form and disposition of the spicules 
differ so much from those of any other genus, that, though ranged 
under the Hexactinellidze, it would be better placed as the type of 
a distinct order; and, finally, in the genera Hyalosteha, Zitt., 
and Holasterella, Carter, there is an extraordinary diversity in the 
form and size of the spicules. These facts clearly show that the 
structure of the principal genera of Paleozoic sponges varies widely 
from that of more recent types of the class, and materially lessen 
the weight of any objections which may be urged against the in- 
clusion with them of the Receptaculitide. 
V. GeotosicaL Disrripurion. 
The earliest known member of the group has been described by 
Billings from the Calciferous (Ordovian or Lower Silurian) of the 
Mingan Islands, Lower St. Lawrence. In the Trenton limestone 
of Canada, and its equivalent, the Magnesian or Galena limestones 
of Illinois and Wisconsin, examples of Receptaculites are abundant, 
and the genus Jschadites makes its appearance here, and in Lower 
Llandeilo beds in Wales. eceptaculites also occurs in the Ortho- 
ceratite limestone of Esthonia and in Lower ? Silurian of the Arctic 
regions. 
In the higher division of the Silurian proper, the genus Ischadites 
is the most abundant. Itis present in Wenlock and Ludlow strata 
in North Wales ; in the Dudley and Malvern areas ; in the island of 
Gotland and the Russian Baltic provinces ; in the Niagara group of 
Ohio, Wisconsin, and Illinois, and at a slightly higher horizon 
at Gaspe, Gulf of St. Lawrence. Receptaculites is present in the 
Upper Silurian of Australia, and doubtfully also in Canada. The 
genus Acanthochona occurs in the Silurian proper, Etage E. of Bar- 
raude, in Bohemia. 
In the Devonian formation the genus Receptaculites is present in 
the middle division; in Mudstone Bay, Devonshire ; in Belgium, the 
Kifel district, and also in the Rhenish province on the right side of 
the Rhine ; at Ober-Kunzendorf in Silesia, and in Canada. The 
genus Spherospongia occurs in Devonian limestones near Plymouth, 
also in Nassau and the Hifel, in Germany, and in the Urals, in Russia. 
Ischadites has not yet been found in the Devonian. 
From Carboniferous strata only a single species of Receptaculites ? 
from Silesia has been recorded by F. Romer, and no member of the 
group appears at any higher horizon. 
All the examples of this family occur in limestone or in fine ecal- 
careous shales or mudstones, which probably indicate a habitat of 
deep or moderately deep water. It is evident, also, from the perfect 
manner in which the lightly attached spicules are preserved in their 
respective positions that the organism must have lived and been in- 
terred at undisturbed depths. 
