24 OUR COMMON BRITISH FOSSILS. 



Generally, however, they are of a stony character 

 and solid everywhere, except in the pure white 

 chalk. 



The Ventriculite family of sponges are hexactinellid, 

 and their shapes and structures are often very beau- 



Fig. 18. Ventriculite. 



tiful, a slight magnifying power showing a similar 

 latticed appearance to that we admire so much in 

 the modern "Venus' flower-basket" (Euplectella). In 

 the white chalk of Sussex, Wiltshire, and Norfolk, 

 Ventriculites occur in great numbers, Ventriculites 



