136 



OUR COMMON BRITISH FOSSILS. 



Fig. 1 14. Fossil 



Marstoni] (Lower Ludlow rocks). 



sea-water. A large star-fish, called Leptychaster, 

 allied to our Luidia, was brought up off Cape Maclear, 

 Kerguelen's Island, in very deep water. Another 



genus, Hymenaster, was 

 found widely distributed 

 over the sea-floor, and 

 at depths ranging from 

 about half a mile to more 

 than three miles. Star- 

 fishes and their allies, the 

 sea-urchins, are usually 

 the commonest fossils 

 of the Chalk formation, 

 which was an oceanic 

 deposit formed under similar circumstances to the 

 "globigerina ooze" of the Atlantic. Dr. Wallich 

 showed (when sounding in the Bull Dog for the first 

 Atlantic cable) that the ocean floor was occupied by 

 star-fishes, for these animals came up attached to the 

 sounding-lead, and this incident first broke people's 

 faith in the old-received notion that absence of light 

 in the deep sea rendered it a desert for all animals 

 except the Protozoa. 



The Asteroidea (represented by our common " five- 

 fingers "), and the Ophiuridea or " brittle-stars," as we 

 have said, are found in Cambrian rocks. Specimens 

 are often better preserved in the fossil state than 

 dried recent specimens usually are in museums. Sea- 

 urchins also lived in the Palaeozoic epoch, but they do 



