736 CLASS xn. 



Sp. Unio pictorum LAM., Mya pictorum L., STURM Faun. Germ. vi. Heft 2, 

 Tab. a, Unio rostrata PFEIFFER Deutsche Land- und Wassersclm. i. Tab. v. 

 fig. 8; Unio margaritiferus RETZ., NILSON, Mya margaritlfera ii., Unio 

 sinuata LAM. (and Unio elowyata LAM.), SCHROETER Geschichte der Fluss- 

 conchyl. 1779, 4to, Tab. iv. fig. i, PFEIFFER 1. 1. Tab. v. fig. u, &c. This 

 species, like the Meleagrina, produces fine pearls (see above, p. 688). As 

 a very large species from N. America we note: Unio undidatus SAY, 

 Unio Peruviana LAM., Encycl. meth., Vers. PI. 248, fig. 7, VALENCIENNES 

 in HUMBOLDT et BONP. Obs. de Zool. et d'Anat. comp. u. p. 229, PI. 54, 

 % 3- 



Anodonta BRUG. The inhabitant of the shell (Limncea POLI) 

 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 dcpressa V. MUEHLFIELD (PFEIFFER 1. 1. n. s. 32, 

 33, Tab. vili. 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., BLAINV. Malac. PI. 66, fig. 

 i, PFEIFFER 1. 1. i. 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, &c. 



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 

 STUTCHBURY (Unio hybrida, Unio concinna SOWERBY, &c.). See STUTCH- 

 BURY Annals and Magaz. of Nat. Hist. vili. 1842, pp. 481 485. 



Iridina LAM. Animal with lobes of mantle concrete poste- 

 riorly and furnished with two short tracheae. Shell transverse, 

 elongate, with hinge edentulous, linear, sometimes crenate. 



Sp. Iridina, exotica LAM., Le mutel ADANSON, Hist. nat. du Senegal, Co- 

 quillages, PL 17, fig. 21, BLAINV. Malac. PL 66, fig. 3, in West Africa and 

 in the Nile ; the animal is described and figured by DESHAYES, Mem. de la 

 Soc. d'Hist. nat. de Paris, ill. 1827, pp. i 16, PL i; Irid. rubens DESK., 

 Anatina rubens LAM., Encycl. meth., Vcrs. PI. 201, fig. i.. 



Phalanx IL Shell affixed, irregular. 



Etheria LAM. (^Etheria). Mantle cloven, with margin cirri- 1 

 ferous. Four tentacles round the mouth oblong, rotundate. Liga- 



