42 GEOLOGICAL MEMOIRS. 



among tliose that were determined ; but a great part of the species 

 of insects from the amber, noted in this manner by the Breslau en- 

 tomologists, probably agree with those of which Behrendt has given 

 a list, and thus the number of amber insects seems larger than it 

 really is. A great part of the genera of plants and fish are founded 

 merely on leaves, stalks, and fruits, or on scales, teeth, and fin-spines, 

 so that one species may appear not only in three genera, but also 

 under three to six specific names. Many plants especially are enu- 

 merated under peculiar names, although their fossil remains cannot 

 be distinguished from certain hving genera, and hence must be united 

 with them (Pinites, Pinus — Acerites, Acer, tS:c.) ; and the fossil 

 ferns particularly are divided into genera from the form of their 

 leaves, which, were the fructification of all of them known, might 

 perhaps fall under those genera which have been established for the 

 existing ferns. The views of the different palaeontologists who have 

 been engaged on these remains, and several of vrhom will not admit 

 of any species common to the living and extinct creation, or to differ- 

 ent periods or even formations, have had great influence on the nomen- 

 clature, which has again affected the following collected results. 



Finally, were even the whole of these difficulties attaching to the 

 preparation of such a work overcome, a third class of them would 

 still remain, preventing us from instituting a just comparison between 

 the former organic world and that which now exists. They depend 

 on this, that we do not know even the actual creation accurately 

 enough, that we know still less accurately all that portion of former 

 creations which lies buried in the bosom of the earth, and lastly, 

 that the part which is here buried represents but very imperfectly 

 the whole which once existed. Many soft naked animals are al- 

 together unfit for becoming fossilized, as the greater number of 

 infusoria (soft polygastrica, as the rotatoria), the entozoa, the aca- 

 lephae, naked annelids, tunicatee, and other molluscs, even some 

 scaleless, cartilaginous fishes. In other animals a whole series of 

 favourable conditions must be combined in order to their preserva- 

 tion in the strata of the earth, so as to be recognizable in after-times. 

 Remains of land-animals and land-plants can only reach the water 

 by accident so as to become imbedded in the strata deposited from 

 it ; even when arrived there, except in very rare cases, we could never 

 expect the soft cellular tissue of plants and animals, but merely, in 

 favourable circumstances, of the former the wood}- fibres of the vas- 

 cular plants, of the latter the horny parts — more readily the earthy 

 portions of the skeleton, as bones, spines, teeth, scales, shells, poly- 

 pidom, bucklers, — to be preserved either immediately and continu- 

 ously, — or at least so long that they should form an enduring im- 

 pression, whether sufficient or insufficient for identifying them. Cal- 

 careous strata are peculiarly favourable for the preservation in a de- 

 terminable condition of calcareous and siliceous remains ; siliceous 

 strata for that of woody bodies ; clays for vegetable substances in 

 general, and the horny (chitine) portions of the animal kingdom ; 

 whilst in sand and sandstone strata almost no calcareous, in lime- 

 stone almost no vegetable remains can be preserved. In order, there- 



