074 riuH-KKDixan or TIII-: \.rno.\.u. MUSEUM. 



Genus MARGARITAN A Schumacher, 1817. 

 (Type, Mya maryaritifera Linna-ua. ) 



Bapln' MKUSCHKN, Mus. (levers, 1787, i>. 472. 

 I'nio RET/ITS, part, Diss. Hist. Nov. Test. Gen., 1788, p. 16. 

 I'nio OKKN, Lehrbuch der Nat., 1815, p. 236. 

 Maryaritana SCHUMACHER, Essai Nouv. Syst., 1817, p. 137. 

 />w7i.s (LEACH manuscript) GRAY, Pr. Zool.Soc. Lond., 1817, p. l!Hi. 

 II. and A. ADAMS, Gen. Kec. Moll., II, 1857, p. 499.' 



Shell elongated, usually arcuate, rounded in front, almost lacking a 

 posterior ridge; beaks rather low, the sculpture consisting of a few 

 coarse, parallel ridges, which follow the growth lines; epidermis con- 

 centrically striate, brownish or blackish; hinge teeth generally imper- 

 fect or not fully developed; two more or less perfect pseudocardinals 

 in the left valve, and one in the right, often reduced to mere tubercles; 

 behind these the hinge plate is narrow and rounded for some distance; 

 laterals short, usually imperfect or wholly wanting; cavity of the beaks 

 rather shallow; muscle scars large, those of the anterior roughened, 

 posterior elliptical; nacre generally more or less covered inside the pal- 

 leal line with small muscle scars. 



Animal with very long gills, inner wider in front, free for the greater 

 part of their length from the abdominal sac, the two pairs united to their 

 posterior ends, which project backward for some distance unconnected 

 with the mantle; palpi very large, falcate, united half way posteriorly ; 

 branchial opening having crowded, often arborescent papilla* arranged 

 in folds; anal opening smooth or crenulate; superanal opening not 

 closed below; marsupium occupying the entire outer gills.- Foot and 

 abdomen small ; whole animal dark colored. 



fMARGARITANA MARGARITIFERA Linnaeus. 



Mya margarilifera LISTER, Hist. Auiru. Aug. App., 1685, pi. i, fig. 1. Hist. 

 Conch., 1685, pi. CXLIX, fig. 4. -* LINN.KUS, Systema. Nat., 10th od., I, 

 1758, p. 671. * DA COSTA, Hist. Nat. Brit., 1778, p. 225, pi. xv, fig. 33. 

 ( i.M KLIN, Syst. Nat., 13th ed., 1792, p. 3219. '* LINN.K rs, Fauna Suecica, 1761, 

 p. 2130. KNORR, Vergn., IV, 1769, pi. xxv, fig. 2. *MI'LLER, Vermes, 1774, 

 p. 210. PENNANT, Brit. Zool., IV, 1777, pi. XLIII, fig. 18. * DA COSTA, Hist. 

 Nat. Brit., 1778, p. 225, pi. xv, fig. 3. k SC.HROTER, Fluss Conch., 1779, p. 168, 

 pi. iv, fig. 1. *BORN, Test. Mus. Viiid., 1780, p. 21. * SCHROTER(Ein. Conch., 

 1783, II, p. 606. * DONOVAN, Brit. Shells, III, 1801, pi. LXXIII. * MONTAGU, 

 Test. Brit., 1803, p. 33. *TrjRTON, Brit. Fauna, 1807, p. 146. * MATON and 



I The name Bapliia- Meuschen has precedence, but was never described ; it was applied 

 to a miscellaneous lot of bivalves, and is in the plural number. Retzius' first species 

 in I'nio, the type of a section without laterals, is the I'. maryaritifer, but in 1792 

 Brugniere in Choix de Me"moires, I, p. 106, fully and carefully redefined the genus 

 Unio, restricting it to species with cardinal and lateral teeth. 



-According to VanWahl. I have examined a great many animals taken at different 

 seasons, but have never seen one; gravid. 



II Refers to Conchylien Cabinet VI, pi. i, fig. 5, which is the form we know as Mar- 

 garilanu maryaritifera. 



