22 Contemporary Appearance of Classes of Invertebrata. 



ancient fossiliferous formations ; and if we have not hitherto 

 discovered any Medusae, it is much more natural to ascribe 

 their absence to their extreme softness, than to suppose that 

 they did not accompany, in ancient times, the types of the 

 other classes of invertebrate animals, with which we always 

 and everywhere find them associated in the presently- exist- 

 ing creation. Some of them, indeed, have been found at So- 

 lenhofen. With regard to insects, their existence has been 

 already ascertained in the coal-formation, which, in my opi- 

 nion, is much more intimately connected with the palceozoic 

 than with the secondary formations, by the whole of its or- 

 ganic characters. It is, therefore, now demonstrated, that 

 all the classes of invertebrate animals have appeared on the 

 surface of the globe at the same time, and that they go back 

 to the most ancient geological epochs; whence it follows, in 

 a manner the most unquestionable, that we can no longer 

 continue to regard them as forming a progressive series in 

 their appearance, as has been so long imagined. For the de- 

 tail of facts, and the nominal enumeration of species, I refer 

 to the important works of Murchison, De Verneuil, D'Archiac, 

 De Keyserling, and Roemer, on the palseozoic formations and 

 their fossils ; reserving for myself only a fevv observations on 

 the vertebrate series, when I come to speak of the fossil fishes 

 of the old red sandstone in particular. 



Our actual knowledge of fossil Polypiers, taken as a whole, 

 not being yet so far advanced as that of the living species, and 

 the Acalephae not having hitherto been observed, except in 

 a few secondary deposits, I think I may dispense with speak- 

 ing of them in this place, without any apprehension of there- 

 by weakening the general results which flow from the par- 

 ticular examination of the other classes of invertebrate 

 animals. 



The interesting researches of MM. Miller, Goldfuss, 

 D'Orbigny, Th. and Th. Austin, J. Miiller, and Leop. de 

 Buch, on living and fossil Crinoides ; those of MM. J. E. 

 Gray, J. Miiller, and Troschel, on the Asterise and Comatulse; 

 my own, and those of MM. Valentin and Desor, on the living 

 and fossil Echinidse, including their anatomy ; those of Profes- 

 sor E.Forbes, and my own, on the Echinoderms in general, and 



