DR. G. J. HINDE ON RECEPTACULITIDA. 801 
genus Ischadites. The authors express no opinion on the characters 
of these fossils, and refer to the hollow casts of the spicules as cells. 
J. W. Salter, in the ‘ Catalogue of the Cambrian and Silurian fossils 
in the Geological Museum of the University of Cambridge’ (1873), 
givesafigure of [schadites Kenigit, Murch., from Dudley, representing 
it with a short cylindrical stem and diverging rootlets, and states that 
it is one of the regular sponges, like Sphwrospongia, and that it pos- 
sesses a root and a foramen at the top, after the manner of Grrantia. I 
may here remark that the stem and root represented as belonging to 
this specimen are probably imaginary, since neither in the Museum 
at Cambridge nor in the Jermyn Street or British Museum is there 
a single example showing traces of any basal stem, nor is such an 
appendage presented in the numerous and perfectly preserved 
examples of this species which occur in the isle of Gotland. 
In 1875 an important treatise on the organization and syste- 
matic position of Receptaculites *, by Dr. C. W. Giimbel, appeared in 
the ‘Abhandlungen der k. bayer. Akademie der Wissenschaften.’ The 
author’s observations were based on examples of R. Neptuni, Defr., 
from Devonian strata in Belgium and Silesia, and he considers the 
original form of these bodies to have been open cup-shaped as they 
are now found, and not conical with a small central aperture, as 
supposed by Billings. By making sections through specimens, 
Giimbel was enabled to ascertain more thoroughly their interior 
characters, and to add further particulars of their structure to those 
made known by Billings. Both the outer and inner surfaces of the 
organism are stated to possess a very thin layer, now of a carbona- 
ceous material, but originally probably of a leathery or horny con- 
sistency. The contact margins of the plates of the outer surface are 
stated to be uneven, and provided with minute sinuosities, which 
probably indicate the presence of small canals, thus allowing com- 
munication between the interior of the organism and the outer 
medium. The surface-plates are said to consist of three distinct 
layers—(1) a thin coaly surface-layer; (2) an upper layer of 
calcite ; and (3) an under-layer of the same substance. This under- 
layer, if I understand correctly Gumbel’s explanations, consists of 
the four radiating arms at the ends of the pillars, with canals in 
the centres of each, which are termed the epistyle. The radiating 
arms of the epistyle are stated not to connect directly with those 
of adjoining epistyles, but to rest side by side. The inner termi- 
nation of the pillars, according to Gimbel, is not furnished, like 
the outer, with an epistyle of four arms, but they possess a greater 
number of thick irregular branches with subdivisions. These are 
never intergrown with the main plates of the inner integument, 
which are said to be strongly folded in the interior. Further, the 
plates of the inner surface of this species are said not to possess 
the circular canals described by Billings in R. occidentalis, but are 
covered with small warty elevations indicating the presence of cells. 
Giimbel agrees with Billings that the interspaces between the 
* Beitrage zur Kenntniss der Organisation und systematischen Stellung von 
Receptaculites; Abhandl. k. bayer. Akad. Wiss. Band xii. Abth. i. pp. 170- 
215, Pl. A. 
