BIBLIOGRAPHY. 21 



114. 1872 Holl, H. B. Notes on Fossil Sponges (Geol Mag., vol. ix, pp. 309— 



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. 



115. 1872 Dewalque, G. Un Spongiaire nouveau du systeme Eifelien (Bull. 



Acad. Roy. de Belglque, T. 34, pp. 23—26, PI. 1). 

 Describes and figures a new species of Astrceospongia. 



116. 1872 Pomel, A. Paleontologie de la province d'Oran, 5 Fasci. (Spongiaires, 



pp. 1—256, 36 pis.). 

 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) Gamptospongiaires , 

 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 Dictyoscleroses, 

 which appears to be equivalent to hexactinellids, and Psammo scleroses, 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 Dictyoscleroses, 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. 



117. 1872 Murchison, 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. 



