70 CONCHOLOGY. 
A. Ferussacina. Lea. A. Wahlamatensis. Lea. 
A. fluviatilis. 2 A. Wardiana. if 
A. Newtonensis. i A. gibbosa. Say. 
A. Nuttalliana, * A. grandis. + 
A. Oregonensis. a A. impura. 4 
A. ovata. A. suborbiculata. 5s 
A. pavonia. i A. undulata. “ 
A. lugubris. 3 
4. Genus Jridina. PI. VIII. 
Animal. As above. 
The principal difference between the Anodonta and the 
Iridina, consists in the tuberculated hinge of the latter. 
Shell. Thin, oval, much elongated, inauriculated ; hinge very 
long, linear, and crenulated throughout its length, ligament ex- 
ternal and marginal; two distinct muscular impressions. Inhabits 
the Nile and American coasts. Six species. 
Iridina exotica. Iridina Nilotica. 
I. celistis.* I. elongata.* 
I. rubens.* , I. McMurtria.* 
FAMILY XIV. 
Cuamacea, ‘Three genera. 
1. Genus Diceras. Pl. VIII. 
Animal. 
Shell. Inequivalve, adherent ; beaks conical, very large, diverg- 
ing in irregular spiral contortions; hinge with a large, thick, 
concave, subauricular tooth in the larger prominent valve; two 
muscular impressions. One species. Fossil. 
Diceras arietina. 
2. Genus Chama. Pl. VIII. 
Animal. Body suborbicular terminated superiorly by a sort of 
hook; mantle very slightly opened for the passage of a foot, termi- 
