Further Work in Kansas Chalk 119 



are never found. According to Mr. Springer, when 

 death overtook one of these swarms, it fell to the 

 bottom, where the first individuals were buried in 

 the soft mud and preserved, while the others, not 

 being so protected, disintegrated. The limy plates 

 of the calices and those of the arms, which were thus 

 mingled together above the perfect specimens, be- 

 came compressed into a hard slab, in the bottom of 

 which the perfect specimens are firmly impressed. 



Great numbers of these creatures have been dis- 

 covered in the English chalk, but they consist only 

 of the disintegrated plates. 



