NO. 1205. SYNOPSIS OF THE NAIADES— SIMPSON. 797 



looped; surface of tlie shell generally covered with eoarse nodules or 

 knobs; posterior slope radially ridged; epidermis dark; two strong 

 laterals in each valve, all vertically striated ; cavity of the beaks deep 

 and compressed; nacre mostly whitish, usually radially grauularly 

 striated outside the pallia! line, having one or more peculiar calluses 

 behind and below the laterals which are iridescent aud granularly 

 striate. 

 Animal unknown.^ 



(Group of Quadrula plumbea.) 



Shell rounded, slightly angulated behind the ligament, solid, moder- 

 ately inflated, covered with coarse pustules, and having broken, up- 

 curved corrugations on the posterior slope; epidermis light brownish; 

 hinge rather strong, somewhat flattened ; laterals vertically striated.^ 



QUADRULA PLUMBEA Chemnitz. 



*Chama plumhea Chemnitz, Conch. Cab., XL, 1795, p. 237, pi. cciii, tigs. 1991, 

 1992.— 'Dill WYN, Cat. I, 1817, p. 215.— * Wood, Ind. Test. Eev., 1856, p. 52, 

 pi. IX, fig. 6. 



Unio plumleus Ferussac, Guer. Mag., 1835, p. 28. — *Kuster, Conch. Cab. Unic, 

 1862, p. 289, pi. xcvii, figs. 1, 2. 



South East Asia, probably. The locality, "South Sea," given by 

 Chemnitz is, no doubt, erroneous. 



t QUADRULA COREANA von Martens. 



*Unio coreanus von Martens, S. B. Nat. Fr., 1886, p. 78. — ^P^etel, Conch. Sam., 

 Ill, 1890, p. 149. 



Soul, Korea. 



(Group of Q. nodulosa.) 



Shell very solid, oval or rounded, inflated, inequilateral, inequivalve, 

 the valves more or less twisted on their axis or having the appearance 

 as if one of them had been pushed forward on the other, so that a dorsal 

 view shows the outline to be rhomboid ; each valve with a posterior 

 ridge, that on the valve pushed forward less developed; beaks high, 

 full, apparently sculptured with a few coarse irregular ridges ; i)osterior 

 slope usually having strong, radiating, upcurved ridges; hinge plate 

 generally wide and flattened ; pseudocardinals heavy, somewhat radiate, 

 often with the sockets evenly, radially grooved; laterals strong, heavily 

 vertically ridged; secondary lateral of right valve well developed, 



' A group of peculiar and striking species which presents a number of quite diverse 

 forms. On account of this diversity, the fact that the beak sculpture is rarely pre- 

 served, and that nothing is known of the anatomy, the group is a difficult one to 

 arrange. 



2 A single, rather young, dead, and somewhat decayed specimen of what I believe 

 is Q. coreana, from Soul, Korea, belonging to the collection of F. Stearns has been 

 examined by the writer. The Chama plumhea of Chemnitz seems to be near it, but 

 is solider and shorter. 



