828 DR. G. J. HINDE ON RECEPTACULITID#. 
however, afterwards relinquished this comparison, and ranged this 
genus under Sponges. Even accepting Giimbel’s own definition, 
that the skeleton in this genus consists of outer and inner walls 
composed of individual plates supported by pillars extending be- 
tween them and enclosing the sarcode, there does not appear to be 
any feature distinctively resembling foraminiferal structure, for no 
undoubted Foraminifer possesses walls of individual plates and a rela- 
tively enormous interior cavity without any partition into chambers. 
If, however, in Receptaculites no resemblance to Foraminifera is mani- 
fest, still less support for this comparison is afforded by the structure 
of the other genera of the family, in which, as we have seen, there 
is no skeletal inner wall. 
It cannot be said, however, that those who advocated the relation- 
ship of this family to Sponges brought forward any satisfactory 
proofs of the alliance. Thus, for example, Spherospongia tessellata, 
Phill. sp., was regarded by Dr. Bowerbank and Mr. Austin as a 
calcareous sponge, on the ground that the spicular plates of the outer 
surface were similar in structure and arrangement to those of 
Dunstervillia (Sycandra, Hack.) elegans, though there is no reason 
for supposing that the plates of Spherospongia, like those of Dunster- 
villia, were made up of a multitude of microscopic acerate spicules ; 
and further, whilst in the former genus there are large spicular 
rays beneath the plates, in the latter there are cylindrical or conical 
tubes bounded by spicules; nor can any definite homology be 
shown between the structure of Receptaculites and its allies and 
that of the gemmule of fresh-water sponges, with which it was 
compared by Mr. Billings. Independently of the enormous dispro- 
portion in size, in no case do the minute birotulate spicules of these 
latter bodies assume the regular form of the spicules in the 
Receptaculitide, that is of a summit-plate, with four horizontal rays 
beneath, and an elongated vertical ray either terminating freely 
or connected with a continuous inner plate. It is only in the 
genus Ischadites, moreover, that there is an approximation in outer 
form to the gemmule of Spongilla, for we have seen that m 
Acanthochonia, Receptaculites, and probably also in Spherospongia, 
the outer form is either cup- or platter-shaped. 
But though Mr. Billings’s comparison of Receptaculites to these 
minute gemmulz cannot be entertained, yet to him is due the merit of 
having recognized a resemblance between what he termed the cylin- 
drical shaft and stolons of this genus and the spicules of sponges. 
He states * that ‘each tube, with its cylindrical shaft and plate at 
- each extremity, resembles not remotely a birotulate spiculum, or it 
might perhaps with more probability be described as consisting of 
two spicula united at their points. Thus the ectorhinal plate with 
the four stolons may be a peculiar form of the foliato-peltate spicule. 
The cylindrical shaft may be a spiculum approaching the acuate or 
acerate varieties, with its point inserted into the nucleus of the 
foliato-peltate spiculum.” 
The knowledge that has been gained in the last few years of the 
* Pal. Foss. Can. p. 387. 
