OF CONCHOLOGY. 23 



Crenulated margin. That fine saw- 

 like edge of most of the cockles, which 

 unite into the notch in the opposite 

 valve. It is by no means uncommon 

 in other shells, particularly the Donax. 

 Plate 4th, fig. 6th, m m. 



Stride are fine thread-like lines, gene- 

 rally on the exterior surface of shells, 

 and is sometimes both longitudinal 

 and transverse, and likewise oblique. 

 In some instances the insides of shells 

 are striated ; for example, the Murex 

 Tulipa. It is often of much use in 

 distinguishing species. Plate 2nd, 

 fig. 2nd,/. 



Right Valve is that valve which, 

 when viewed with the inside towards 

 you, the anterior slope points to your 

 right hand. Plate 1st, fig. 8th ; and 

 plate 4th, figures 5th and 6th, B. 



Left Valve. The opposite of the 

 above ; the anterior slope points to 

 the left hand, when viewed from the 



