Harvey B. Holl — On Fossil Sponges. 67 



The former- contained but a single genus, Cliona ; the latter he subdivi- 

 ded into five families, based entirely upon external characters, viz.: 

 1, the OceUarid(c ; 2, the Siphonida^ ; 3, the Lymmrklce; 4, the ^par- 

 sispongidcc; and 5, the Amorphospongidce. At the same time he pro- 

 posed many new genera. These were constituted partly of species 

 which had been distributed by his predecessors among genera estab- 

 .lished on recent forms by Lamarck and Sehweigger, and adopted for 

 fossil species by Dr. Goldfuss. 



Pictet, and more lately De Fromen telle, have followed D'Orbigny in 

 the view which he took respecting the stony character of the skeleton 

 of the fossil sponges. The Fetrospongida; of Pictet, and the Spongitaria 

 of the French author, correspond to the " Amorpliozoaires a squelette 

 iestaci " of D'Orbigny. M. Etallon also entertains the same view. 

 He includes among the fossil horny sponges none but the Clionidre ; 

 and in speaking of the Petrospongidce observes, that the skeleton is solid 

 " like that of the Zoantharia, and formed doubtless in the same man- 

 ner," In fact, nearly all the authors, with the exception of ]MM. Cap- 

 ellini and Pagenstecher, appear to entertain similar views respecting 

 the nature of the skeleton in this large group of fossil species. D'Or- 

 bigny and De Fromentelle maintained that the fossil sponges had origi- 

 nally a solid, unyielding skeleton. This opinion was partly based on 

 the supposition that they would not otherwise have escaped compres- 

 sion, and partly on the circumstance that Polyzoa, Serpulse, Ostreidaj, 

 etc., frequently found attached parasitically to the surface of the sponge, 

 have been observed to exhibit the worn appearance produced by the 

 rolling of hard bodies on the sea bed. Moreover, they say that com- 

 pressed specimens show more or less distinctly the signs of fracture. 

 But while this may be true of some of those sponges that had a solid 

 siliceous framework, it certainly is not generally the case, and exam- 

 ples of Hippalimus, Ischadites, Moiiierxa, and many other sponges, 

 more or less distorted by compression, are sufficiently abundant. That 

 they should not — especially the cup-shaped sponges — be more often 

 compi-essed than they are, may perhaps be a matter of surprise. But 

 this is probably due to the circumstance that the fine muddy sediment 

 in which they were entombed had so insinuated itself into the inter- 

 spaces of the sponge as to afford an equal amount of support on all 

 sides. [The compression often observed in fossils, especially those of 

 the older rocks, is probably due to the squeezing to which they have 

 been subjected in the change of position and contortion of the beds in 

 which they occur, rather than to the dead weight of the superimposed 

 sediment. It is now well known that starfish and other soft animals, 

 even at the great depths of mid ocean, are not compressed, owing to the 



