BIBLIOGRAPHY. 21 
114, 1872 Hott, H. B. Notes on Fossil Sponges (Geol. Mag., vol. ix, pp. 8309— 
115. 
116. 
17. 
315, 343—352). 
Refers to the general characters of fossil Sponges, and points out the 
artificial nature of the classification of D’Orbigny and Fromentel. The 
following conclusions are given: (1) That the present state of fossil Sponges 
affords no certain indication of their condition during life, and (2) that in 
the differentiation of genera and species the same principles must be kept in 
view in fossil as in recent Sponges. 
1872 Dewatquy, G. Un Spongiaire nouveau du systtme LHifelien (Bull. 
Acad. Roy. de Belgique, T. 34, pp. 23—26, Pl. 1). 
Describes and figures a new species of Astrw@ospongia. 
1872 Pomet, A. Paléontologie de la province d’Oran, 5 Fasci. (Spongiaires, 
pp. 1—256, 36 pls.). 
The untenability of the theory of D’Orbigny and Fromentel that fossil 
Sponges are altogether distinct from recent forms is fully recognised. Pomel 
divides the class Spongiaires into two primary groups: (1) Camptospongiaires, 
in which the spicules when they exist are isolated and not organically attached 
together, and (2) Petrospongiaires, in which the skeleton is a continuous tissue 
of stony consistency. This latter group is again divided into Dictyoscléroses, 
which appears to be equivalent to hexactinellids, and Psammoscléroses, forms 
with skeletons of a granular or vermiform texture. In this latter order the 
author distinguishes two families, one with a calcareous and the other with 
a siliceous skeleton. As regards the skeleton of the Dictyoscléroses, or hexacti- 
nellid Sponges, Pomel maintains the same opinion as Roemer that the spicular 
tissue has in all cases originally been siliceous and that in the instances in 
which it is now calcareous the change has been produced by molecular 
displacement. Pomel thus appears to have been the first to recognise the 
substitution of calcite in the place of the original silica in the skeleton of fossil 
Sponges. The smaller subdivisions of Pomel are based upon the position and 
character of the so-called ‘ Proctides,’ and most of the genera of previous 
authors are split up on very insufficient grounds. Numerous genera and 
species, apparently both of hexactinellid and lithistid Sponges, are described 
and figured, but their spicular characters are not referred to. 
1872 Muroutson, R. I. Siluria, 5th ed. 
In the table drawn up by Mr. Etheridge showing the vertical range of the 
Silurian Fossils of Britain, there are enumerated (p. 509) seventeen species of 
Amorphozoa, but ten of these are either doubtful forms or belong to other 
groups. 
