120 



tions, or teeth *, the distinguishing character of the genus. 

 The singular rising in the middle of the upper shell, of about 

 5 pleats wide) and the corresponding cavity in the under 

 one, is a curious character, common, with some variations^ 

 to both these and the Anomia, with which they have gene- 

 rally been confounded. The little Anomiae at the bottom 

 are darker, and probably contain more iron. Their struc- 

 ture is certainly remarkable, especially as we, in the present 

 age, have no recent shells in this part of the world at all 

 corresponding with them. We think these the more in- 

 teresting on that account, as they help to indicate, that at 

 certain periods there were some animals very different from 

 those now existing. 



These were sent me from the Tees by the Rev. Mr. Har- 

 riman, and also by Mr. Winch, in large fasciculi. They 

 are found in other parts, but I do not know how near the 

 present surface of the earth. 



They are but little crumbly in their fracture, rather con- 

 densed, and approaching to the conchoidal, like flint : they 

 are often very tough, but too heavy for building, and not of 

 any known utility at present : they, perhaps, might be liable 

 to decay, as the ochraceous substance is somewhat scattered 

 through them. They sometimes contain more or less clay. 



* See Area, t. xv. p. 35. 



