TO GEOLOGY. 63 



A. parva. Plate 2. Fig. 37. 



Description. Shell triangular, rounded below, acutely 

 angular above, compressed, equilateral, concentrically and 

 closely striate ; beaks elevated, pointed ; lunule large, 

 lanceolate ; cardinal teeth small, the posterior margin fur- 

 nished with a long straight lateral. one ; cicatrices scarcely 

 visible ; margin crenulate. 



Diam Length .1, Breadth .1, of an inch. 



The smaller figure is of the size of nature. 



Observations. Although this and the two following spe- 

 cies do not accord entirely with Sowerby's generic descrip- 

 tion of Jlstarte, nor that of Lamarck under the name of 

 Crassina, inasmuch as these have a long, straight, lateral 

 tooth ; I have preferred placing them there, as they agree 

 in all the other generic characters, thinking it unnecessary 

 to make a new genus for them. 



The species above described is more elevated and more 

 acutely angular at the beaks than the others. Its striae 

 are much finer, and it is supposed to be emarginate imme- 

 diately under the point of the beaks. 



w3. minor. Plate 2. Fig. 38. 



Description. Shell triangular, rounded below, angular 

 above, compressed, equilateral, concentrically and" widely 

 striate ; beaks elevated, pointed ; lunule large, lanceolate ; 

 cardinal teeth small, the posterior margin furnished with 



