316 GEOLOGICAL SURVEY OF THE TEREITORIES. 



Cretaceous, also representing typical forms of our living species. Their 

 presence in the Tertiary is attested, as far as we know yet, by four 

 species. The oaks of our living flora, with the great diversity of forms of 

 their leaves, have, also, their primitive types in species of the Cretaceous. 

 One type, that of the leaves with entire borders, like Quercus FJiellos, Q. 

 Iml)ricaria, being distinctly marked, especially in Q. salieifoUa, Newby. ; 

 Q. anceps, Lsqx. ; Q. .EllswortJiiana, Lsqx., while the type of the chestnut- 

 oaks is essentially represented by Q. ^rimordialis, Lsqx. The same types 

 traverse our Tertiary flora, and there multiply in the nineteen species of 

 Tertiary forms, analogous, some of them at least, to species distributed 

 at our time in Northeastern and in ISTorthwestern America. For the 

 beach, the leaves of our Cretaceous species, also diversified in forms, 

 while traversing the Tertiary, are scarcely distinguishable from those of 

 the living species. Even the chestnut appears to be represented in the 

 Cretaceous by a species which I refer to Quercus, viz, Q. Mudgii, on. 

 account of the branching of a few of the secondary veins, but which is 

 a true Gastanea by the divisions of the leaves. After this we have in 

 our Cretaceous, with fewer but well specified representatives, BeUila in 

 B. Beatriciana, Lsqx., Alnusor Corylus in alargeleaf Alnus (?) grandifoUa, 

 iN'ewby.; Ficus in leaves of a type recognizable in numerous forms of this 

 genus in our Tertiary, with species of Laurus, Sassafras, and Cinna- 

 niomun, all, except the last, types of living species of the North Ameri- 

 can flora. One of the three forms of sassafras of our Cretaceous is, by 

 its leaves, undistinguishable from our living species. The genus Plata- 

 nus also has its Cretaceous type preserved to our time with scarcely any 

 variation of form in one species, which I have referred to P. aceroides, 

 Gopp., and which is scarcely distinguishable from our P. occidentalis. In 

 the Tertiary we know already a number of remarkable species of this 

 genus, which now has a single representative on our continent, and is 

 apparently disappearing from the present flora. 



The -second section of the dicotyledonous, the monopetalous, is not 

 largely represented in North America by arborescent species. We have 

 especially shrubs. However, Biospiros and Andromeda have their types 

 marked in the Cretaceous. And in the third section, the polypetalous, 

 our Liriodendon, Magnolia, Acer, Bliartinus, Aralia, Juglans, even appa- 

 rently Prunus, whose species are still predominant, have all typical 

 representatives in the Cretaceous of ours. 



It would be interesting to pursue these researches with more details, 

 and to follow some specific forms in their development through the Ter- 

 tiary ; but mere descriptions are insufficient without figures for such a 

 kind of comparison. 



Some of our now living species, of course, have not as yet any recog- 

 nized types in the Cretaceous, perhaps, because the researches have not 

 been pursued over a wide extent of this formation. Nevertheless, these 

 Cretaceous leaves of ours have a, fades with which some of the present 

 forms do not agree. They are all either entire, or lobed, or with borders 

 merely undulate. No serrulate or doubly serrate leaf has been recog- 

 nized among them, and, as far as it is known till this time, all the genera 

 whose species have leaves of this kind, like Alnus, Carpinus, Ostrya, Ul- 

 mus, (?) Fraxinus, Vitis, Tilia, are not in the Cretaceous. The large 

 leaf referred to TJlmus, (?) by Dr. Newberry, has the borders undulately 

 and obtusely lobed ; even the Cretaceous species of Acer are merely 

 three-lobed, with obtuse lobes and entire borders. It will be interest- 

 ing to study the apparent absence of these forms in the Cretaceous, and, 

 if real, to observe in the Tertiary the origin of what we may call a new 

 type and the transitions to it. 



