IN DESCRIBING SHELLS. 27 



a long square with the corners rounded off, as Tellina 



radiata. 

 Triangulatus, triangular, as Mactra siibtruncata. 

 Cordatus, heart-shaped, but compressed thin, as Cardium Car- 



dissa. 

 Tuinguceformis, tongue-shaped, long, and rather tapering, as 



My a Vulsella. 

 Cuneiformis, wedge-shaped, as Donax cimeata. 

 Auricidatus is with two small appendages or wings, called by 



Linnaeus ears, as in Ostrea maxima, the common Scallop 



ipl. 4. /. 41). 



OF THE PARTS OF BIVALVE SHELLS. 



First, of the Beaks. 

 Nates or Umbo, a beak, is a blunt point which may be seen 



on the outside of each valve near the hinge. 

 Incurvatus or Inflexus is when the beaks are curved inward, 



as in Area Glycymeris. 

 Recurvatus or Rejlexus is when the beaks are curved back- 

 ward, as in Chama Cor. 

 Approximatus is when the two beaks are near together, or 



stand approaching to each other, as Cardium Cardissa. 

 Distans is when the two beaks stand at a distance from each 



other, as in Cardium Hemicardium. 

 Remotissimus is when they stand at a greater distance from 



each other, as in Area Noce. 

 Prominulus is when the beaks are but little prominent, or 



e2 



