GINGLYMACONCHA. AMPHIDESMADZ. 274 
Pandora obtusa, Leach, MSS. Lam. Hist. Nat. des Anim. 
sans Vert. v. 499. 
This species was first discovered by Mr. Lyons at Tenby ; it 
has since been found by Mr. Loscombe in Torbay, and in the 
Plymouth Sound by Mr. J. Cranch and C. Prideaux, Esq. 
FAMILY VII. AMPHIDESMAD. 
The shell somewhat elongate or subtriangular, gaping a little 
before and behind ; the umbones nearly central or behind the 
middle of the shell; the cardinal ligament interior. 
* Umbones pone teste medium locatt. 
Cardo in valva dextra lamella ante et 
poue umbones 52.6) .: ss... 20. AMPHIDESMA: 
** Umbones subcentrales. 
Cardo in valvis ambabus lamellee ante et 
pone umbones ....... : 27. EUPOLEME. 
Cardo invalva sinistra aatallte ante at 
Pouerminbones 22050. S22 S922) © 28) OREA. 
Caro lamellis nullis’. 0) 0/0 oe 29> TRIGONELEAS 
Genus 26. AMPHIDESMA. 
Amphidesma, Lamarck. 
The shells rather elongate ; the umbones situated behind the 
middle of the shells ; the hinge with a lamella before and behind 
the umbones in the right valve, and without lamelle in the 
left valve: the process bearing the cardinal ligament is pro- 
duced vertically. 
The upper margin of the left valve (in all the species) before 
and behind the lamella bearing the cardinal ligament is very 
much attenuated, and is received into the grooves formed in the 
opposite valve between the margin and the Jamelliform teeth. 
