11 
Besides these, we have, however, in the chalk other forms no 
longer represented: the huge Ichthyosaur and Plesiosaur, the 
flying Pterodactyie, a gigantic lizard—the Mosasaurus, a genus 
represented in the American cretaceous, where it is associated with 
other extinct genera of Reptiles, and some existing types of Tortoises 
and Crocodiles. All these and other genera so characteristic of 
Mesozoic times, became extinct at the close of the Chalk period. 
Fragments are occasionally found of once floating wood, indicative 
of some adjacent land, bored, however, by the Teredo before it 
became waterlogged.* 
Other evidences point, if rightly interpreted, to varying climatal 
conditions ; for while the general nature of the deposit and its remains 
infer a warm or subtropical ocean, the discovery, about 18 years 
since in your neighbourhood, in the chalk-pit near Purley, of a block 
of granitoid rock with associated fragments of greenstone and sand, 
led Mr. Godwin-Austen to believe, from its size, that it was not 
floated in by means of drift wood or seaweeds, but that upon some 
ice-bound northern shore, and fallen from the cliffs above, it 
became encased in shore ice, with the sand of the beach, and 
was subsequently floated away and deposited in a more southern 
region, just as the boulders are now carried by icebergs from 
Greenland, and dropped when brought into the influence of the 
warm gulf stream. The mass of sand and blocks presented 
such an assemblage as now might be found on a beach on the coast 
of Norway, in latitude 60° north.+ Nor is this a solitary instance, 
for, although sand, pebbles, and drift wood are not common in the 
white chalk, still pebbles are sometimes found; and some years 
since Mr. Willett noticed a rounded block, 13-lbs. weight, in the 
upper chalk of Lewes, to which were attached Spondylus lineatus, 
some Serpule, and Bryozoa; and in the lower cretaceous beds, near 
Cambridge, blocks of various sizes and of northern origin are 
frequently found, to which are attached some characteristic shells of 
cretaceous age. |} 
* The scarcity of the remains of a land vegetation in the upper cretaceous rocks 
of England and France, and their comparative abundance and peculiar character in the 
equivalent strata of other parts of Europe and of the United States, is a suggestive and 
interesting fact ; for the tertiary aspect of the upper cretaceous flora of Colorado (the 
Dakota group), and Greenland is also represented in Europe, in Bohemia, Saxony, the 
Hartz, and at Aix-la-Chapelle, where, in the Aachenian sands, Dr. Debey has noticed and 
described about 400 species of plants, the larger number belong to Dicotyledonous angio- 
sperms, associated with some conifers (sequoia &c.), and about 80 species of ferns. (See 
Prof. Lesquereux, ‘‘The Cretaceous Flora of the Western Territories,” 1874. Also the 
“Memoirs of Prof. Heer and Dr. Debey.”) 
+ Quart. Journ. Geol. Soc., vol. xiv., p. 252. 
t Rev. O. Fisher, in alluding to the change of the Lower Cretaceous rocks in 
Cambridgeshire, says :—‘‘ A glance at a geological map of England will show the out-crop 
of the secondary rocks thereabouts making a semi-circular sweep, having the old rocks of 
Charnwood Forest in the centre, We have also a Paleozoic slaty rock within about a 
thousand feet of the surface at Harwich. If these two points be joined by a line curving 
slightly northward, just parallel to the axis of the weald, such line will represent the 
direction of the slight elevation to which the curvature of the out-crop of the secondary 
rocks is due, and will pass through the area where the character of the Lower Cretaceous 
rocks changes from nodule bed and gault into Red Chalk. A second Paleozoic ridge 
following that direction would account for this change (several of the erratic pebbles of 
