Br. H. B. Soil — On Fossil Sjjonges. 311 



tion, has been long felt. This renders it desirable to discover, in the 

 minuter structure, characters of a more permanent nature. With 

 respect to the living sponges this has indeed been done, more or 

 less successfully, by Dr. Bowerbank. He finds " in the skeleton and 

 in the form and disposition of the spicula, characters which, how- 

 ever Protean the form and colour of the sponge may be, can always 

 be recognized with certainty." Can the same means be made avail- 

 able for the extinct species ? Obviously there will be many difficul- 

 ties in the way, for in the latter we have to deal with the skeleton 

 alone, modified by fossilization ; whereas in the former all the 

 structures are in a condition admitting of minute investigation. 

 Nevertheless, very commonly enough of the minute structure can 

 be made out in the fossil to render it a most important means of 

 discriminating the species. The external appearance is all but 

 valueless for this purpose. 



II. Prior to the time of D'Orbigny, no attempt had been made to 

 systematize the genera established by Lamoureux, Goldfuss, De 

 Blainville, Michelin, Eeuss, and others. M. D'Orbigny, however, 

 conceiving that the fossil sponges had, for the most part, an organi- 

 zation entirely distinct from that of the recent species, divided De 

 Blainvdlle's class Amorphozoa into two orders, viz., the horny and the 

 stony sponges. The former contained but a single genus, Cliona : 

 the latter he subdivided into five families, based entirely upon 

 external characters, viz., 1. the Ocellaridce ; 2. the Siphonidce ; 3. the 

 Lymnoreidce ; 4z. the Sparsispongidoe ; and 5. the Amorpliospongidaz. , 

 At the same time he proposed many new genera. These were con- 

 stituted partly of species which had been distributed by his pre- 

 decessors among genera established on recent forms by Lamarck and 

 Schweigger, and adopted for fossil species by Dr. Goldfuss. 



Pictet,' and more lately De Fromentel,^ have followed 

 D'Orbigny in the view which he took respecting the stony character 

 of the skeleton of the fossil sponges. The Petrospongidce of Pictet, 

 and the Spongitaria of the French author, correspond to the 

 "Amorphozoaires a squelette testace " of D'Orbigny. M. Etallon 

 also entertains the same view. He includes among the fossil horny 

 sponges none but the GlionidcB; and in speaking of the Petro- 

 spongidce observes that the skeleton is solid, " like that of the 

 ZoANTHARiA, and formed, doubtless, in the same manner."^ In fact 

 nearly all authors, with the exception of MM. Capellini and 

 Pagenstecher,* appear to entertain similar views respecting the 

 nature of the skeleton in this large group of fossil species. 



D'Orbigny^ and De FromenteP maintained that the fossil sponges 

 had originally a solid unyielding skeleton. This opinion was partly 



1 Paleont., iv. 2nd ed. ^ E'ponges Fossiles, 1859. 



2 Classification des Spongiaires du Haut Jura, and E'tudes Paleont. sur le Haut 

 Jura, p. 139. 



* Mikroskopische Untersuchungen ueber den innern Bau einiger fossilen Schwamme 

 Z. W. Z., etc. 



» " Qu'ils n'ont jamais He comes, mais que leur tissu a toujours ete calcaire et 

 pierreuse." Cours Elementaire de Pale'outologie, torn. it. p. 208. 



s I. c, p. 5. 



