MACTRA. 85 



the front margin thin and plain, the upper edges on each 

 side the hinge thick and flattened, and gradually curving on 

 both sides : hinge with a spoon-shaped cavity in one valve, 

 and a thin oblique tooth each side ; in the other a similar 

 cavity, with a triangular tooth on one side, and a thin ob- 

 lique one on the other, without lateral ones : in young 

 shells are two prominent sharp transverse teeth in one 

 valve, receiving the triangular tooth of the other between 

 them : length two inches and a half; breadth four and a 

 half. 



Variety. Of a more oblong shape, being three times as 

 wide as it is long, with the margins forming nearly a 

 straight line, and about half the size. The specimen under 

 our examination was dredged up at Cove, near Cork, and 

 in the teeth and general appearance exactly resembles a 

 more produced variety of this species. 



At the mouths of rivers, w. . 



14. Mactra hya-ns. Oblong Macira. Fig. 41. 



Da Costa, pi. 17- f. 4 Donovan, pi. 140 Dorset Cat. 

 pi. 2. f. 4 - Linn. Trans, vi. pi. 16. f. 5, 6. 



Shell oblong-oval, thick, strong, nearly opake, rounded 

 and somewhat gaping at the larger end; the anterior side 

 elongated, a little contracting and curving in a somewhat 

 scymetar-shaped form, the end considerably gaping, with a 

 slight angular tendency : color dull white, with a reddish 

 yellow tinge towards the hinge : beaks near one end, 

 pointed and incurved, from which there is a considerable 

 slope or indenture towards tbc smaller end, and a strong 

 groove which runs along the margin on the outside ; from 

 the beaks is also a depressed line on the outside extending 

 to the lower end of the front margin ; inside dull white, 

 with a ferruginous patch under the hinge on the broader 

 side, the margin plain and thin : hinge with a spoon-shaped 

 cavity and two plain laminar teeth behind it in one valve ; 

 in the other two teeth behind the cavity, one of which is 

 thick and cloven, the other thin and plain ; lateral teeth 

 none : length, of the specimen before us, two inches and 

 three quarters ; breadth five inches and a half. 



This elegant shell is readily distinguished from M. Lu- 



traria, by its elongated and rather &cymetar-shaped form ; 



I by 



