730 CLASS XII. 
Comp. Lamarck Ann. du Muséum, ul. pp. 25—31, Pl. 2. 
Sp. Orenatula avicularis Lam. 1.1, Pl. 2, figs. r, 2, Cuv. R. Ani., éd. ill., 
Moll. Pl. 81, fig. 2; in the seas surrounding the South American coasts. 
Vulsella Lam. Shell irregular, elongate, thin, subequivalve, 
free. Hinge in both valves furnished with a tubercle cut out 
with a conical pit for receiving the ligament. 
Sp. Vulsella linguatula Lam., Mya vulsella L., Rumen. Amb. Rariteitk. Tab. 
46, fig. a, Buarnv. Malacol. Pl. 62, fig. 5, from the Indian ocean, &e. 
Some species are met with amongst corals, others in sponges. One 
species from the tertiary formation is known (Vulsella deperdita Lam., from 
the calcaire grossier), and a few from the chalk-period. 
Malleus Lam. Shell subequivalve, rude, often undulate, de- 
formed, elongate, flattened, auriculate, emarginate anteriorly for the 
passage of byssus. Straight, triangular, sinus between the two 
valves; points small, divaricate. Hinge edentulous; cardinal 
fossula oblongo-conical, receiving the ligament. 
Sp. Malleus vulgaris LaM., Ostrea malleus L., Rumpa. Amb. Rariteitk. Tab. 
47, fig. 11.; D’ARGENVILLE Conchyliologie, 1757, 4to, Pl. 19, fig. A, 
Buainv. Malac. Pl. 63, fig. 4; this shell, commonly called the Polish 
Hammer, is found in the East-Indian Ocean. On account of its rarity in 
collections, Malleus albus Lam., CHEMnitz Conchyl. Tab. 206, from the 
South Sea, may be noticed. 
Avicula Bruc., DesHAyes, Shell subequivalve or inequivalve, 
often squamose externally. Hinge edentulous or with one or two 
small teeth. Area oblique, submarginal, sometimes subindistinct 
for the internal ligament. Internal surface of valves pearly. 
Animal compressed, with mantle open, the margin incrassate, 
cirriferous. Foot conical, vermiform, with byssus thick, the fila- 
ments sometimes coalesced. 
Sub-genus: Avicula Lam. Shell oval, oblique, with ears large. 
A cardinal tooth in both valves beneath the points. 
Sp. Avicula semisagitta Lam., Mytilus Hirundo L. in part, Buatny. Malac. 
Pl. 63, fig. 8;—Avic. Tarentina Lam., Pout Testac. utr. Sic. Tab. 32, figs. 
17—21, &c. Fossil species also from the Muschel-kalk and other formations 
are known. 
Meleagrina Lam. Shell suborbicular, with ears not produced and 
hinge edentulous. 
Sp. Avicula margaritifera, Mytilus margaritiferus L., Rome. Amb. Rari- 
teitk. Tab. 47, figs. F, ¢; D’ARGENV. Pl. 20, fig. A, Buainv. Malac. Pl. 
