30 TERMS USED 



Thirdly, of the Margin. 



That part of the margin which is opposite the beaks 

 (^pl. 3. f. 26. h) is often called the upper margin, or margo 

 superior ; and, as the cartilage is considered by Linnaeus as 

 occupying the anterior parts of the shell, so that part of the 

 margin which lies between the beaks and the end, on the side 

 where the cartilage is found Qil. 3. f. 26. c), is called the 

 anterior margin, and that between the beaks and the other 

 end (p/. 3. /. 26. rf) the posterior margin; the hollow or 

 cleft that is occupied by the cartilage is called riina anterior. 

 The margin is said to be integerrimus when it is smooth 

 without any notch or w^rinkle, and is opposed to dentatiis, 

 serratus, &c., as Donax cuneata, Vemis Chione, &c. 

 Acutus is when the margin is smooth, but thin and sharp, as in 



Mactra stultornm. 

 Dentatus is when the margin has small wrinkles, called teeth, 



as in Donax denticulatus. 

 Serratus is when the margin is toothed like a saw, as in Car- 



diuni serratum. 

 Crenatus is when the margin is wrinkled or notched, with 



larger wrinkles than dentatus, as in Area Glycymeris. 

 Plica^s is when the wrinkles are still larger, like plaits or 



folds, as in Area Pectunculus and senilis. 



OF UNIVALVE SHELLS. 



The Univalve spiral shells are said to be involute or con- 

 volute. 



