GEOLOGY OF MY GARDEN. 



23 



textuluria (2), polymorphina (3), lagena (4), globigerina (5) ; and also 

 that nodosaria (6) was represented by many of its very beautiful 

 varieties. There are also other forms of foraminifera much resembling 

 miniature ammonites and nautili (7). 



The revelations of the microscope showing to us how chalk was 

 formed in times gone by, and how it is being formed by similar 

 creatures at the present time (fig.. 22), are certainly not the least 

 interesting results of modern science. 



The chalk in our district is not highly fossiliferous. The chalk- 

 diggers tell me, the deeper they go the less they find. Many old books 

 state that fish have been found fossilized in the chalk near Croydon. 

 Mr. Flower kindly lent me one (fig. 23) to figure, from Riddlesdown, 

 but they do not appear to be very common. Mr. Herbert Jackson, when 

 the cutting was made for the Sutton Railroad, watched the proceedings 

 and obtained several species : one was a tooth of a kind of shark 

 (fig. 24), called the Corax falcatus. Some bivalve shells were found, 

 such as the Rhynchonella plicaiilis (fig. 25), and the Terebratula semi- 

 globosa (fig. 26). 



Fig. 25. — Rhynchonella 

 plicatilis. 



Fig. 24.— Tooth of Corax falcatus. 



Fig. 23. — Fossil fish's head, \ real size. 



Fig. 26.— Terebratula 

 semiglobosa. 



All over the Downs curious things, known to the country people as 

 shepherd's crowns, are found, which are diiiferent kinds of echini. 

 Two forms of one kind are found of Galerites albo-galerus (fig. 27) ; 

 .1 have also figured a flint cast of Holaster pillula (fig. 28), and a 

 specimen of Pseudo Diadema variolare (fig. 29). All these are varietie? 

 of sea-urchins or echini, one species of which is constantly seen on 

 our sea-coasts, demonstrating the marine origin of chaJk. . 



