106 MYA. 



THICK GAPER. 

 PL 20 and 21. Mr. Jennings. 



28. Mya crassa. M. testa ovata, antrorsum angustata, umbonibus decor- 

 ticatis. 



Shell oval, narrow before, urabones decorticated. 



A thick shell covered with a rough dark brown 

 epidermis, except near the hinge, where it is completely 

 decorticated. The shell is truncated towards the car- 

 tilage slope, and undulated from the hinge to near the 

 margin. The margin is smooth. The inside is pearly, 

 and the hinge is furnished with a very strong crenated 

 tooth, which fits into a similar depression in the op- 

 posite valve ; the lateral teeth are extremely thick and 

 rough ; there are two in one valve and one in the other. 

 The muscular depressions are deep and crenated. This 

 massy shell, figured from a specimen in the splendid 

 cabinet of Mr. Jennings, weighs a pound and six 

 ounces, and measures three inches and a half in length, 

 and six inches in breadth. Its country is unknown. 



KNOTTED GAPER. 

 PL 22. /. 1, 2, 3, 4. Mr. Jennings. 



29. Mya nodulosa. M. testa subovali, valvulis nodulosis ; cardinis 

 dente crasso, crenulato. 



Shell somewhat oval, valves knotted ; hinge with a thick crenated tooth. 



This species is remarkable for the knots with which 

 the outside of each valve is studded. In some places 

 these knots are perfectly distinct, but near the margin 

 they unite, and form waved ridges. This shell is of a 

 bottle-green colour, and more or less decorticated about 

 the hinge. The inside is pearly, and the teeth, like 



