736 CLASS XII. - 
Sp. Unio pictorwm Lam., Mya pictorum L., Sturm Faun. Germ. v1. Heft 2, 
Tab. a, Unio rostrata Preirrer Deutsche Land- und Wasserschn. 1. Tab. v. 
fig. 8;—Unio margaritiferus Retz., Nitson, Mya margaritifera L., Unio 
sinuata LAM. (and Unio elongata LAM.), SCHROETER Geschichte der Fluss- 
conchyl. 1779, 4to, Tab. Iv. fig. 1, Prerrrer 1. 1. Tab. v. fig. 11, &c. This 
species, like the Meleagrina, produces fine pearls (see above, p. 688).—As 
a very large species from N. America we note: Unio undulatus Say, 
Unio Peruviana Lam., Encycl. méth., Vers. Pl. 248, fig. 7, VALENCIENNES 
in Humeoupt et Bonr. Obs. de Zool. et d’' Anat. comp. Il. p. 229, Pl. 54, 
fig. 3. 
Anodonta Bruc. The inhabitant of the shell (Zimnea Port) 
of the same form as the animal of the preceding genus. Shell 
mostly thin, transverse, elongate posteriorly, rotundato-truncate 
anteriorly. Cardinal margin edentulous, linear. 
River-mussel. This genus differs from the preceding in the greater thin- 
ness of the shell, and especially by the absence of hinge, but the animal is 
entirely the same as in the genus Unio, with which too DESHAYES unites it. 
In the shell also Unio depressa V. MUEHLFIELD (PFEIFFER 1. 1. II. s. 32, 
33, Tab. vil. figs. 3, 4) forms the transition to Anodonta. The species of 
Anodonta are much less numerous, and exhibit fewer varieties in the form 
of the shell, than those of Unio. 
Sp. Anodonta cygnea Lam., Mytilus cygneus L., Buarnv. Malac. Pl. 66, fig. 
1, Preirrer 1.1. 1. Tab. vi. fig. 4, (on account of the coalescence or 
growing together of the shells on the dorsal side above the ligament, LEA 
forms of this species and some others, the genus Symphynota; such a con- 
nexion also occurs in certain species of Unio); Anod. anatina LaM., Myti- 
lus anatinus L., PFEIFFER Tab. VI. fig. 2, &e. 
Fossil species both of Unio and Anodonta occur in the coal-formation. 
In the Oolite and Lias shells are found which were formerly referred to 
Unio, but now constitute the genus Cardinia of Agassiz, Pachyodon 
SrutcuBury (Unio hybrida, Unio concinna SowERsy, &c.). See StutTcH- 
BURY Annals and Magaz. of Nat. Hist. vit. 1842, pp. 481—485. 
Iridina Lam. Animal with lobes of mantle concrete poste- 
riorly and furnished with two short trachee. Shell transverse, 
elongate, with hinge edentulous, linear, sometimes crenate. 
Sp. Jridina exotica Lam., Le mutel ADANSON, Hist. nat. du Sénégal, Co- 
quillages, Pl. 17, fig. 21, Buatny. Malac. Pl. 66, fig. 3, in West Africa and 
in the Nile; the animal is described and figured by DesHAyEs, Mém. de la 
Soc. d’ Hist. nat. de Paris, 111. 1827, pp. I—16, Pl. 1;—Jrid. rubens DESH., 
Anatina rubens LaM., Encycl. méth., Vers. Pl. 201, fig. 1. 
Phalanx II. Shell affixed, irregular. 
Etheria Lam. (Atheria). Mantle cloven, with margin cirri- 
ferous. Four tentacles round the mouth oblong, rotundate. Liga- 
