﻿5l8 MARCARITANA 



have never seen this kind of nacre in specimens from other 

 parts of the area of distribution of the species, but I do not 

 think such a variation worthy of a varietal name. 



MargariTana crassa (Retzius). 



Shell large, solid, arcuate, sometimes subrhomboid, often 

 rounded in front and behind, inequilateral, not inflated, beaks 

 moderately elevated but not full ; surface w^ith irregular growth 

 lines ; epidermis bfcackish in old shells, brownish-green or red- 

 dish-brown in younger ones, dull ; left valve with one or two 

 strong, irregular, ragged pseudocardinals and two, sometimes 

 three remote, rather small laterals ; right valve with a single 

 pseudocardinal, sometimes with a vestigial tooth behind it, 

 and one lateral ; beak cavities moderately deep ; muscle scars 

 large, impressed, the anterior rough, the posterior smooth and 

 elliptical : pallial line deep, often rough ; nacre white, sHowmg 

 pits occasionally of the muscular attachment of the mantle. 



Length 137, height 67, diam. 40 mm. 



Length 126, height 69, diam. 33 mm. 



Length 134, height 63, diam. 38 mm. 



Southern Europe ; possibly into Asia Minor and southwest 

 Siberia. 

 Mya testa crassa SchroTer, Flussconch.. 1779, p. 182, pi. 11, 



fig- 2. 

 Margaritana crassa Simpson, Syn.. 1900, p. Gyy. 

 Unio crassns Retzius, Diss. Hist. Nat., 1778, p. 17. 

 Margaron (Unio) crassns Lea, Syn., 1852, p. 39; 1870, p. 62. 

 Unio aitriciilariits SpKugler, Skriv. Nat. Siesk., in, 1792, p. 54. 

 Unio riigosa Poiret, Coq. Fluv.. et Terr, de I'Aisne, 1801, p. 



54- 

 Unio sinuata Lamarck, An. sans Vert., VL 1819, p. 70. — 



Bi.AiNViEEE, Man., 1825, p. 539, pi. lxvii, fig. 3.— Deshayes, 



Enc. Meth., H, 1827, p. 151. pi. ccxeviii, fig. i ; IL 1830, p. 



579, pi. ccxTvViii, fig. I, a, &. 

 Unio fPotamida) sinuata Swainson, Tr. on ^lal, 1840, p. 268. 



