460 



MESOZOIC TIME. 



Sterribergii Lsqx., Sassafras Mudgii Lsqx., S. mirabilis Lsqx., S. obtusus Lsqx., S. re- 

 curvatus Lsqx., Laurophyllum retictdatum Lsqx., Platanus Heerii LsqK.^Pterospermites 

 ( Credneria) Sternbergii Lsqx., Pt. Haydenii Lsqx., Pt. rugosus Lsqx., Salix proteifolia 

 Lsqx., Betula Beatriciana ~Lsqx., Fagus polycladus Lsqx., Quercus primordialis Lsqx., 

 Magnolia tenuifolia Lsqx., Pterophyllum Haydenii Lsqx. (a Cycad). 



2. Animals. 



Among Protozoans, the group of Rhizopods had a special impor- 

 tance in the Cretaceous period. Their shells, foraminifers, are abun- 

 dant in many of the beds, in New Jersey and other Cretaceous regions 

 of North America, though less so than in the chalk beds of Europe. 



Figs. 829-831. 



Rhizopod. 



•Fig. 829, Orbitolina Texana. Brachiopods. — Fig. 

 Terebratula Harlani. 



), Terebratulina plicata ; 831, 



In one genus, Orbitolina, the species are disk-shaped (Fig. 829), and 

 closely resemble in form some of the Nummulites. Sponges also are 

 common fossils, although little known thus far in America. 



Under the sub-kingdom of Mollusks, the most common Brachiopods 

 are of the Terebratula family (Figs. 830, 831). The more character- 

 istic genera of Lamellibranchs were the three of the Oyster family, 

 Ostrea (Fig. 833), Gryphcea (Figs. 835, 836), and Exogyra (Fig. 834) 

 (species of which occurred in the Jurassic period, but were more com- 

 mon and larger in the Cretaceous), and Inoceramus (Fig. 837), a 

 genus related to Avicula,, some species of which are of great size, and 

 have the surface in undulations. 



Another group characteristic of the Chalk period, and, moreover, 

 not known after it, is that of the Rudistes (Figs. 862-866). It in- 

 cludes the genera Hippurites, Radiolites, Sphcerulites, and a few others. 

 Hippurites has a long tapering form (Fig. 862), somewhat like a 

 nearly straight but rude horn, with a lid on the top, the lid being the 

 upper valve and the conical portion the lower. Within, there is a 



