Dr. G. J. Hinde—Spicules in Archeocyathus, 227 
Meek,! Dawson,” Ferd. Roemer,? Bérnemann,! Walcott,’ and Schliiter,® 
but it cannot as yet be said that any satisfactory or decisive con- 
clusion as to its character and affinities has been arrived at. Mr, 
Billings’s statement as to its spicular structure has considerably 
increased the perplexity of the subject and influenced opinion in 
favour of its alliance’? to sponges; any fresh information therefore 
respecting the nature of these spicules and their relation to the fossil 
Archeocyathus, may help to remove an element of uncertainty in the 
consideration of the question as to its true nature. 
Fig L 
PAWsonye, 
Fig. 1. Detached spicules of siliceous sponges occurring in specimens of Archeocyathus 
Minganensis, Billings, and the so-termed branching spicula of the same fossil. 
a, Acuate spicule, showing traces of the axial canal. 4, ¢, d, Different forms 
of acerate spicules ; in () the axial canal is partially preserved. e, Fragment 
of a cylindrical spicule showing the axial canal. All enlarged to the same 
scale of 40 diameters. f, g, h, 7, Silicified fragments of the outer wall of 
A. Minganensis, the so-called ‘branching spicula’’ of Billings. Reduced 
from Billings to the scale of 40 diameters. 
Through the kindness of Sir J. W. Dawson, F.R.S., I have been 
supplied with a small quantity of the original material obtained by Mr. 
Billings through treating fragments of rock containing Archeocyathus 
with acid, and from which the spicules were procured, which, as 
already mentioned, have been described and figured as probably 
belonging to this fossil. The coarser portions of this residual débris 
are irregular-shaped siliceous fragments, of a grey tint, showing in 
1 American Journ. of Science, n.s, vol. 45 (1868), p. 62; vol. 46, p. 144. 
2 Life’s Dawn on Earth, p. 164. 
5 Letheea Paleeozoica, p. 301. 
4 Versteinerungen der Insel Sardinien (1886), p. 28. 
> Cambrian Faunas of North America, Bull. No. 30, U.S. Geol. Surv. (1886), p. 72. 
® Zeitsch. d. deutsch. Geol. Gesellsch. 1886, p. 899. 
7 Thus we find one of the latest writers on it, Mr. C. D. Walcott, stating that the 
presence of spiculz in this species associates it with the Spongiz, close to the family 
Euretidse of Zittel, and he considers that the spiculze ‘‘in several of the species have 
been lost in the crystallization of the calcite now forming the skeleton,’’ /.c. p. 80. 
