322 GINGLYMACONCHA. UNIONID. 
1. DAMARIS ELONGATA. 
Shells with their valves obtusely angulated, slightly pressed 
together above and widely emarginated below ; the epidermis 
black or fuscous black. Length five inches; height two inches 
and a half. : 
Mya margaritifera, Lister, Anim. Angl. App. t.i. f.1; Coneh. 
exlix. f. 4; Linn. Faun. Suec. 2130; Syst. Nat. xu. 1112. 
no. 29; Penn. Brit. Zool. iv. 80. t. xlu. f. 18; Drap. 
Hist. Nat. des Moll. terrest. et fluv. 133. t. u. f. 5, yanior ; 
Da Costa, Brit. Conch. 225. t. xv. f. 3°; Donov. Brat. 
Shells, t. lxxiii.; Mont. Test. Brit. 33; M. & R. Trans. 
Linn. Soc. viii. 40; Flem. Edinb. Encycl. vii. 87 ; Wood, 
Gen. Conch. 1. 107. t. xxii.; Dill. Dese. Cat. 52; Turt. 
Conch. Dict. 106. 
Unio elongata, Lam. Hist. Nat. des Anim. sans Vert. vi. 
part. i. 70. 
The shells without the epidermis are pearly, and inside po- 
lished, pearly and rosy. 
Mantle brown, inclining to luteous; its fringe deep brown ; 
orbicular muscle behind the middle, dirty white; the adductor 
muscles whitish ; abdomen silvery white ; branchize dirty lu- 
teous ; foot subluteous, its base lieolated with pale fuscous ; 
lips dirty luteous. 
Inhabits rapid, rocky rivers and torrents. It occurs m the 
rivers Dun or Avon, in the Dart, in the Exe near Tiverton, and 
the Yalm, in Devon ; in several of the Cornish rivers; in the 
river Wye, near Hereford; in the Irt, Cumberland; in the 
Conway, Wales; in the Clyde, in rivers near Perth, and in the 
Tay, Scotland ; in the Ban, Ireland, &c. 
This species is undoubtedly the Mya margaritifera of Lin- 
neeus, as he quotes Lister’s ‘ Historia Concharum,’ t. 149. f. 4, 
where an exact figure is given. 
In young specimens the anterior, lower and posterior margins 
of the valves are submembranaceous and inclining to olive 
colour ; their inner surface is also iridescent. 
This species, in common with its exotic congeners, produces 
