includes more than forty kinds of ferns, besides laurels, figs, magnolias, and other plants, which show that, though the winters were no doubt dark, they must have been extremely mild. There

FIG. 185.-Cretaceous Foraminifera. (a) Textularia baudouiniana (2);
(b) Globigerina cretacea (f); (c) Rotalina voltziana (3).

could have been no perpetual frost and snow in these Arctic latitudes in Cretaceous times.

Foraminifera abound in some of the Cretaceous limestones, indeed, in some places they form almost the only constituent of these rocks. They are plentiful in the white chalk of England, France, and Belgium, one of the more frequent genera being Globigerina (Fig. 185) which still lives in enormous numbers in the Atlantic, and forms at the bottom of that ocean a grey ooze not unlike chalk (Fig. 33). Sponges lived in great numbers in the Cretaceous sea. Their minute siliceous spicules are abundant in the Chalk, and even entire sponges enveloped in flint are not uncommon (Ventriculites, Fig. 186). Seaurchins are among the most familiar fossils of the Chalk, and must have lived in great numbers on the Cretaceous FIG. 186.-Cretaceous Sponge sea-bottom. Some of their genera are still living, and have been dredged up in recent years from great depths in the ocean. Among the more characteristic Cretaceous types are Ananchytes, Holaster, Micraster, and Echinoconus (Fig. 187). The brachiopods were still represented chiefly by the ancient genera Terebratula and Rhynchonella. Lamellibranchs abounded, especially the genera Ostrea, Exogyra, Inoceramus (Fig. 188), Lima,

Pecten, and the various forms of Hippuritids. These last (Hippurites, Radiolites, Caprina, etc., Fig. 189) are specially characteristic, being, so far as we know, confined to the Cretaceous system; hence their occurrence serves to indicate the Cretaceous

FIG. 187. Cretaceous Sea-urchins. (a) Echinoconus conicus, (=Galerites albo-galerus), under surface and side view; (b) Ananchytes ovatus (), side view and under surface; (c) Micraster cor-arguinum (1), upper and under surface.

age of the rock containing them. They have been imbedded in such numbers in the limestones of the south of Europe as to give the name of hippurite - limestone to these rocks. They are comparatively infrequent in the strata of the northern Cretaceous basin.

Probably the most distinctive feature in the molluscan life of the Cretaceous seas was the extraordinary variety in the develop

FIG. 188.-Cretaceous Lamellibranchs. (a) Trigonia aliformis (); (b) Inoceramus sulcatus(); (c) Nucula bivirgata (natural size).

ment of the cephalopods. This is all the more remarkable from the fact that before the next geological period the great majority

FIG. 189.-Cretaceous Lamellibranchs (Hippurites). (a) Radiolites acuticostata (3); (b) Hippurites toucasiana (); (c) Caprina Aguilloni (); (d) Caprotina toucasianus (f).

of these types appear to have become extinct. The ammonites and belemnites, which played so important a part in the fauna of Mesozoic time, died out about the close of that long succession of periods. At least in Europe, while their remains continue to

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FIG. 190.-Cretaceous Cephalopods. (a) Baculites anceps(); (b) Ptychoceras emerici. anus (1); (c) Toxoceras bituberculatus(); (d) Hamites rotundus (); (e) Ancyloceras renauxianus (6); (f) Scaphites æqualis(); (g) Crioceras villiersianus (); (h) Helicoceras annulatus; (i) Ammonites inflatus (1); (k) Turrilites catenatus().

present themselves up to the top of the Cretaceous system, they disappear entirely from the overlying strata. It is curious to observe that while these important tribes were about to vanish, other cephalopods of new and varied types flourished contemporaneously with them. Never before or since, indeed, have the cephalopodan types been so manifold (Fig. 190). For instance, Baculites is a straight chambered shell reminding us of the ancient Orthoceras. In Toxoceras the shell is bent into the form of a bow. In Hamites it is long, tapering, and curved upon itself like a hook. In Ancyloceras it is coiled at the posterior end, the other being bent back upon itself; while in Scaphites the coils are adherent. In Ptychoceras the shell is long, tapering, and bent once back on itself, the two portions being in contact. In Crioceras it is coiled, and the coils are not adherent, as they are in the ammonites. In Helicoceras the shell is coiled spirally, the coils remaining free, while in Turrilites they are adherent.

The fishes of the Cretaceous period are chiefly known by teeth belonging to various genera of sharks (Otodus, Lamna, Oxyrhina).

FIG. 191.-Cretaceous Fish (Beryx lewesiensis, 1).

But they also include the earliest known representatives of the modern osseous or teleostean fishes, such as the herring, salmon, and cod (Osmeroides, Enchodus, Beryx, Fig. 191, Syllamus, etc.)

Already reptilian life seems to have been on the decline, at least there is much less variety and abundance of it in the Cretaceous system than in that which immediately preceded it. Turtles and tortoises continued to haunt the low shores of the time. Ichthyosaurs, plesiosaurs, pterosaurs, and deinosaurs still lived, but in diminishing numbers, and they are not known to have survived the Cretaceous period. One of the most remarkable of the deinosaurs, and interesting from being one of the last of its