CRETACEOUS ANIMALS. 



477 



the Laramie in the Cretaceous we may add 226 more species to the 

 list, but these latter are quite different and Tertiary in type. A few 

 Palms have also been found in Vancouver's Island. 



It is a noteworthy fact that many of the most characteristic Creta- 

 ceous genera, and those most abundant and varied in species at that 

 time, are now represented by only one or two species. For example, 

 there are now only two species of Sassafras ; two or three species of 

 Plane-tree ; one of Liriodendron ; and two of Liquidambar. These 

 are evidently the remnants of an extinct flora. 



Origin of Dicotyls. — The appearance of these, the highest order of 

 plants, in fully differentiated forms, seems sudden and without pro- 

 genitors. But the obvious reason is, that there is here a great loss of 

 record. The gap is now filled by the discovery of the Comanche 

 group ; and in the lowest part of this group on the Atlantic border 

 (Potomac formation), have recently been found and described by Fon- 

 taine 350 species of plants mostly of Jurassic types (Conifers, Cycads, 

 and Ferns), but among them, and from the upper part of the forma- 

 tion, 76 species of Dicotyls. These earliest known Dicotyls, though of 

 very generalized character so far as genera and families are concerned, 

 are yet well-differentiated, unmistakable Dicotyls. We must, there- 

 fore, look still lower for their point of origin and for connecting links 

 with other classes. These important discoveries leave us still in doubt 

 as to the class of previously- 

 existing plants from which 

 they may have sprung. 



But if the highest plants, 

 the Dicotyls, are abundant, so 

 are also the lowest Proto- 

 jrfiytes, or uni-celled plants. 

 Diatoms, Desmids, Cocco- 

 spheres, are abundant in the 

 chalk of Europe. 



Animals. 



/ Protozoa. — As already 

 stated, chalk is made up al- 

 most wholly of shells of Fo- 

 raminiferae (Rhizopods) and 

 of certain uni-celled plants. 

 According to Ehrenberg, a 

 cubic inch often contains 

 millions of microscopic or- 

 ganisms. More than 120 species of Foraminifers have been found in 

 the English chalk alone. Some of these seem to be species still living 



Figs 



776, 777.— Cretaceous Sponges: 

 ficus. 777. Ventriculites simplex. 



Siphonia 



