138 BRITISH PALASOZOIC SPONGES. 
Genus.—RecEpracunites, Defrance. 
1827. Dictionnaire des Sciences Naturelles, tome 45, Atlas, pl. 68. 
Syn.—Coscinopora (in part), Goldfuss, D. Dale Owen. 
Generic Characters.—Cup- or platter-shaped Sponges, growing from a small 
inverted conical nucleus, and frequently reaching considerable dimensions. Wall 
thick, the outer or under surface consisting of rhomboidal spicular plates similar 
to those in Jschadites, and, as in this genus, disposed in decussating lines. The 
four transverse or horizontal spicular rays form radial and concentric lines beneath 
the surface-plates. The vertical or entering ray of the spicules is sub- 
cylindrical, frequently constricted near its junction with the transverse rays; at 
its inner end it expands, to form a small horizontal plate, which is traversed by 
horizontal canals. By the junction of the inner plates with each other a distinct 
inner or upper layer of the Sponge-wall is formed, and in one species at least this 
layer is perforated by cylindrical canals, thus giving communication to the interior 
space of the Sponge-wall. 
This genus is distinguished from all others included in the family by the 
presence of an inner layer formed by the development of small plates at the 
extremity of the entering ray of the spicules. 
Owing in part to the peculiar aspect of examples of this genus under different 
conditions of preservation, various views have been held as to its character and 
affinities. By Defrance and Hichwald the hollow casts of the vertical spicular 
rays were believed to be polyp-cells, and the genus was placed with Corals. 
Salter at first regarded it as a Foraminifer allied to the family of the Orbitolitide ; 
Billmgs placed it with Sponges on account of a supposed resemblance to the 
gemmules of Spongilla; by Dames it was placed a second time with the Foramini- 
fera as the type of a family near the Orbitolitide ; and still later Giimbel retained 
it in the same class, but included it in the family of the Dactyloporide. 
The genus makes its first appearance in the Ordovician of North America, 
Russia, and the Arctic regions; it is present in the Silurian proper at Malvern ; 
Australia, and doubtfully in Canada; in the Devonian of Devonshire, Belgium, the 
Hifel, and elsewhere in Germany as well as in Canada; and a single somewhat 
doubtful species is recorded from the Carboniferous Limestone of Silesia. 
