60 
ROOM VIII. classed by Linneus with the Chama), Hiatella 
Nat. Hist. (Mya of Linneus), and Isocardia. The last ge¬ 
nus includes the rare and elegant shell Isocardia 
Moltkiana—the Chama Moltkiana of Gmelin. 
Table 10. —The families Arcacea, Trigoni- 
ana, and part of the Naiada. Amongst them 
are the Cucullsea auriculifera (Area cucullus. 
Gmel.), several species of the genera Area and 
Pectunculus, and the genus Nucula (the two 
latter were confounded with the Arc^e, by Lin¬ 
neus) ; the genus Trigonia, and part of the ge¬ 
nus Unio (Mya of Lin.), some species of which 
furnish pearls of considerable size and beauty. 
Several new species of Unio from North Ame¬ 
rica, described by Barnes, (in the American 
Journal of Arts and Sciences,) are contained in 
this and the next table. 
Table 11. Unio continued; and the genera 
Hyria, Anadonta (Mytilus, Lin.), and a single 
valve of the Iridina ovata (?) a very rare genus, of 
which Lamarck gives but one species. Also the 
families Chamacea, Tridacnea, and part of the 
Mytilacea. Of the Chamacea, is a specimen of 
the Diceras arietina, the only known species of 
this genus, and hitherto not found as a recent 
shell; also various species of Chama. The se¬ 
cond Order, of this class, Conchifera unimuscu- 
losa, begins with the family Tridacnea, compre¬ 
hending the genera Tridacna and Hippopus.— 
Some shells of the former genus, of the species 
Tridacna gigas, are the largest that are known; 
they are said to have been found of 500 pounds 
weight. 
