DR. G. J. HINDE ON RECEPTACULITID A. ° 835 
after studying very carefully examples of Billings’s type species, P. 
Halli, which I collected myself from Silurian strata at Anticosti, I 
can positively assert that there is nothing in common between the 
structure of this species and that of Spherospongia. Iam also able 
to affirm the correctness of Billings’s latest description of this form, 
that its surface consists of small convex elevations, composed of a 
very thin minutely wrinkled layer, which is sometimes translucent. 
There is no evidence that this surface-layer was divided into distinet 
plates, or that the elevations were perforated. Certainly, in Pasce- 
olus there is nothing to correspond with the spicules of the Recepta- 
culitide, and no analogy appears to me to exist between these forms. 
I may also here mention that two forms placed by Salter in the 
genus Spherospongia, S. hospiialis* and S. melliflua ty, have no 
affinity with the type of this genus, S. écssellatus, Phill. sp., but are 
probably related to Pasceolus, Bill. No reliance can be placed on 
Salter’s figure of S. hospitalis which is evidently diagrammatical 
only. | 
F. Romer has ranked Archwocyathust, Bill., in the Receptaculi- 
tidee from its possessing an outer and inner wall connected by ver- 
tical lamellee which are thought to correspond with the connecting 
pillars, or vertical spicular rays of [teceptaculites. There is, however, 
no real analogy between these structures, and it seems to me pro- 
bable that, if a sponge at all, Archwocyathus will be found to be 
composed of minute spicules similar to those figured by Billings in 
A. minganensis. Archeocyathellus §, Ford, and Protocyathus ||, Ford, 
appear to be closely allied to Archewocyathus. 
I am unable to express any opinion as to the resemblance of the 
genus Goniolina, D’Orbigny 4], to members of this group, since the 
description given of it by that author is limited to the surface- 
characters of the fossil. 
VII. Revision oF THE SPECIES. 
In the absence of any satisfactory generic definitions, the same 
forms have been placed by different authors sometimes in one and 
sometimes in another genus. I have below endeavoured to arrange 
them in accordance with the characters which I have assigned to 
the different genera. It will be seen that in several instances I 
have comprehended in a single species forms which have hitherto 
been placed under several; but the numerous gradational differences 
in minute details of outer form and size in the large suite of speci- 
mens which I have examined, clearly show that these variations 
are not of the specific value which has been placed on them. 
* Cat. of Cambr. & Silur. Foss. Uniy. Cam. p. 40. 
t Pal. Niti, p. 48, t. 5. f. 4, 5, 6. 
t Pal. Foss. Canada, vol. i. p. 354, figs. 342-344. 
§ Amer. Journ. Sci. 1878, vol. v. p. 211. 
| Id. 1878, vol. xv. p. 124. 4 Prodr. de Pal, vol. ii. p. 41. 
