﻿MARGARITANA 519 



Unio sinuatus Rossmassle^r, Icon., Ill, 1836, p. 22, pi. xiii, 

 fig- 195- — I>upuy, Hist. Moll. Fn, 1852, p. 630, pi. xxiii, fig. 



7. — ROSSMASSLER, Icoil., Ill, 1854, p. 38, pi. LXX, fig. 853a. 



— Moquin-Tandon, Moll. Terr, and Fluv. Fr., II, 1855, p. 



567; III, pi. xivViii, figs. 1-3. — Drouet, Nay. Fr., II, 1857, 



p. 61, pi. II. — SowERBY, Conch. Icon., XVI, pi. 1.X11, fig. 311. 



— LocARD^ Coq. de Fr., 1893, p. 151, fig. 164. 

 Margaritana sinuata Ortmann, Naut., XXV, 191 1, p. 6. 

 f Unio Utoralis C. PFiiiFFER, Nat. Deutsch. L. and S. W. Moll., 



Pt. I, 1821, p. 117, pi. V, fig. 12. 

 Unio crassissinms Hanlev, Biv. Shells, 1843, P- 209, pi. 



XXIII, fig. 54. 

 Unio gargottcB Phiuppi, Moll. Sic, 1836, p. 66. — Rossmass- 



LER, Icon., VII and VIII, 1838, p. 26, pi. xxxv, fig. 493. 



The shells of this species bear a strong superficial resem- 

 blance to those of Margaritana ntargaritifera, the latter having 

 been repeatedly mistaken for this form. Usually the epider- 

 mis is duller and blacker than that of margaritifera, the beaks 

 are a little fuller and higher, while the nacre is always white 

 and the laterals are fairly well developed. The muscle scars 

 are much alike in the two species, the anterior ones being rough 

 and the posterior ones regularly elliptical, but in M. crassa the 

 scars of attachment are few or often wanting, while they are 

 generally present and often numerous in margaritifera. 



The M. crassa appears to be confined to Southern Europe, 

 and, judging by the scarcity of specimens in collections, it is a 

 rather rare species. Unio batavus, with which it has been con- 

 founded, is a much smaller and rather more inflated species, 

 which has its metropolis north of that of M. crassa. 



Retzius' description is in Latin, and consists of ten words, 

 and as- he does not figure the species, it would be impossible 

 to determine what he meant only for the fact that he refers 

 to the Flussconchylien of Schroter (Mya testa crassa, p. 182, 

 pi. II, fig. 2). Schroter's figure is not a very good one, but I 

 can have no doubt that he had before him the large, heav^', 

 black Naiad, with lateral teeth, found in southern Europe. In 

 general it closely resembles the M. margaritifera externally, 



