n 



Mr Tate on a Sea Star, &c. 



CRIBELLITES CARBONARIUS. 



(Natural size, from a cast.) 



tion is about 8000 feet in thickness, it is in the upper part of 

 this series of beds. 



Besides this sand star there occur, in this stratum, Stropho- 

 mena crenistria and the remains of plants. This association 

 is of some interest. Numerous marine organisms in the 

 limestones, and in shales connected with them, belonging to 

 the mountain limestone of Northumberland, abundantly evi- 

 dence the deposition of such beds under marine conditions ; 

 but rarely are marine organisms seen in the sandstones which 

 form a large proportion of this formation in Northumberland. 

 Another sandstone, higher up in the series, appearing in a 

 quarry, exhibits, however, a similar association ; it is twenty- 

 three feet in thickness, and has a thin layer one foot thick, 

 which is crowded with Strophomena crenistria ; but both in 



