240 



PICTURESQUE SKETCHES 



Fig. 95 



imagine how an animal provided with so 

 heavy a covering could move about. It 

 may have been permanently attached, 

 though no stem appears, and possibly it 

 was provided with a membrane project- 

 ing between the plates, and coating their 

 external surface. 



The true encrinites are not very com- 

 mon in the chalk, and this is especially 

 the case in our own country. Some re- 

 markable forms occur on the Continent, 

 and one of these is represented in the 

 annexed figure (95), but they are rarely 

 in a perfect state. 



Besides these radiated animals, many 

 others of various kinds, and perfectly en- 

 closed in a stony case, such as sea-urchins, 

 &c., are found in the chalk, especially 

 in particular localities, and are accom- 

 panied by the remains of crabs and lob- 

 sters, some of them belonging to that tribe 

 of hermit crabs (fig. 96) which have no cal- 

 careous cover- 

 ing except up- 

 on the claws, 

 and are oblig- 

 ed to make use 

 of the shells 



of whelks and 

 PAGURUS. other un i va l ve 



mollusca as habitations. It is interesting 

 to be able to trace the similarity of orga- 



BOURGUETI- . , . 



CRINUS. nization which enables us to recognise a 



Fig. 96 



