DR. G. J. HINDE ON RECEPTACULITID.A. 795 
52. On the Structure and Arrinirins of the Famity of the Rucup- 
TACULITID®H, encluding therein the Genera Iscuavtres, Murchison 
(=Terracontis, Aichwald); Spumrosponera, Penyelly; AcAN- 
THOCHONIA, gen. nov.; and Recrrracutites, Defrance. By 
GezorcE Jennines Hinpe, Ph.D., F.G.S. (Read June 25, 1884.) 
[Puates XXXVI, XXXVII.] 
ConrTENTs, 
I. Introduction. 
II. Mineral Structure and Aspect under different Conditions of Fossilization. 
IIL. Characters of the different Genera. 
IV. Affinities and Systematic Position. 
V. Geological Distribution. 
VI. Genera not belonging to the group, but usually included therein. 
VIL. Revision of the Species. 
I. Inrropvuction. 
Amonest the Paleozoic fossils whose characters differ to such an 
extent from those of existing organisms that great differences of 
opinion as to their affinities have been expressed by the various 
paleontologists who have studied them, the above-named genera 
occupy a prominent position. They have been assigned in turn 
to pine-cones, Foraminifera, Sponges, Corals, Cystideans, and Tuni- 
cate Mollusca; but after all that has been written on them, 
such competent authorities as Ferdinand Romer* and Zittelt 
agree in stating that they form an altogether uncertain group of 
organisms, which, though ranged provisionally amongst the Forami- 
nifera, have hardly a single typical character in common with 
them. Under these circumstances a fresh attempt to interpret 
their structure will not be inappropriate ; and though the new facts 
which I have to bring forward do not make any very important 
additions to those ascertained by previous students of the group, 
they at least furnish, in my opinion, striking evidence in favour of 
the affinity of these forms to Sponges. This velo rp has already 
been strongly advocated by the late Mr. Billings ¢; and though the 
basis of comparison which he instituted between the structure of 
Receptaculites and the gemmule of freshwater sponges cannot now 
be maintained, yet in regarding the former as a sponge, Mr. Billings 
showed, in my opinion, a clearer insight into its systematic position 
and structure than later authorities, such as Prof. Giimbel and Dr. 
Dames, who have ranged it with Foraminifera. 
The materials which have served as the foundation for the fol- 
lowing observations have been derived from several sources. First, 
the collection in the British Museum of Natural History, of 
which a list will be found in the ‘Catalogue of the fossil Forami- 
* Tiethea Pal. 1 Th. p. 285. ft Handb. der Pal. 1 Bd. 1880, p. 727. 
-. 4 Pal. Fossils of Canada, vol. i. 1865, p. 388. 
