GINGLYMACONCHA. MACTRADZ. 283 
NvuCULA MARGARITACEA. 
Shell concentrically finely striated, the epidermis elevated 
into obsolete radiating lines ; inferior margin crenate. 
Colour olivaceous, often inclining to testaceous, sometimes 
rayed faintly with pale brown. It is rarely found of a white 
colour. Length five-eighths; height half an inch. 
Arca Nucleus, Pet. Gaz. t. xvi. f. 9; Linn. Syst. Nat. xii. 
1143; Penn. Brit. Zool. iv. 98; Gmel. Syst. Nat. 3314 ; 
Donov. Brit. Shells, t. lxiii.; Mont. Test. Brit. 141; M. & 
R. Trans. Linn. Soc. viii. 95; Flem. Edinb. Encyel. vi. 
91; Dill. Desc. Cat. 244; Turt. Conch. Dict. 8. 
Arca margaritacea, Brug. Encycl. Méth. Vers. 109. 
Nucula margaritacea, Lam. Syst. des Anim. sans Vert. 115 ; 
Hist. Nat. des Anim. sans Vert. vi. pt. 1. 59. 
Glycymeris argentea, Da Costa, 170. t. 15. f. 6. 
Inhabits all our sandy shores, as well as the deep water. 
The concentric striz, and the elevated epidermis, often produce 
a reticulated appearance, especially at the anterior extremity of 
the shell: this is most evident in such shells as have anti- 
quated ridges. 
FAMILY IX. MACTRADZ. 
Teste plis aut minus trigone. Ligamentum internum. 
Cardo angulatus paucidentatus. 
Synopsis Generum. 
Testze cardo dente uno angulato in utraque 
valva, in una integro, in altera fracto ; et 
lamella ante et pone dentes cardinales, in 
una simplici, in alteré duplicata ...... 32. Macrra. 
Testz cardo edentulus, lamellis duabus 
eequalibus, angulum delineantibus, ante 
et pone ligamentum, instructus ...... 33. DoRvILLEa. 
