LIST OF ILLUSTRATIONS. 



Plate I. Large Oyster from Llanduduo, opened on the upper 

 shell, and showing the mantle, c, the adductor muscle, a, 

 the edges of the brouchise, d, and the ovaries, B B. 



Plate II. Dissection of an Oyster : a, ovaries ; b, the situa- 

 tion of the mouth ; c, the labial palpi ; D, D, d, liver ; 

 E, the stomach ; f, the heart ; g, the intestinal canal ; 

 H, the vent. 



Plate III. Fig. 1. Dissection of an Oyster, showing the prin- 

 cipal nerves — a, that communicating with the adductor 

 muscle ; B, that communicating with the mouth. 



Fig. 2. Outline of a Cockle-shell, showing the siphons, 

 B, and the foot, a. 



Plate IV. Figs. 1 & 2. Spawn from the ovary. 



Fig. 3. Spawn from between the folds of the beard. 

 Some of the spawn is of the same form before it is exuded. 



Fig. 4. Spat on the Oyster after it has been detached 

 from the parent and adhered to some foreign substance. 



Plate V. Fig. 1. Oyster opened to show tlie spawn, b, between 

 the folds of the mantle. 



Fig. 2. Tlie hinge and ligament in a large Oyster. 



Plate YI. Oysters from one year old to five. 



