ANOMIA. CONCHIFERA. 77 



at the base, and still more rarely rayed on the external surface. The animal has 

 no foot, no arm, no projecting syphon, and in many genera the shell is fixed upon 

 marine bodies by its lower valve, which is always the largest. 



* Ligament interior ; shell thin, papyraceous. 



Gen. 10. ANOMIA, Lin. 



Shell inequivalve, irregular, operculated, adhering by the oper- 

 culum ; under valve flattened, with a hole or notch near the 

 beak, the upper larger, concave, entire ; operculum small, 

 elliptical, fixed upon foreign bodies, and attached to a muscle. 



The Anomiaa are irregular shells, always fixed to the same place, and are found 

 on other shells, stones, fuci, &c. 



A. ephippium, Lin. Shell suborbicular, with wrinkled plaits and the 

 flat valve perforated ; the summit of the other obtuse ; foramen 

 oval. 3 inches in diameter. Inhabits rocky coasts of Europe. 

 Common. B. Browns Illust. pi. 34, fig. 4. 



A. cepa, Lin. Shell suborbicular, reddish violet, pellucid, rough, 

 rosy red within. 1^ inch in diameter. Inhabits European coasts. B. 

 -Turton, Biv. Brit. pi. 18, fig. 4. 



A. electrica, Lin. Shell suborbicular, yellowish, with the surface 

 slightly undulated ; convex valve gibbous. 1 1 inch in diameter. 

 Inhabits European coasts. Turton, Biv. Brit. pi. 17, fig. 8, 9. 



Gen. 11. PLACUNA, Lam. Anomia^ Lin. 

 Shell free, irregular, flattened, subequivalve ; interior hinge with 

 two longitudinal ribs approximated at their base, and diverg- 

 ing in form of the letter V, and upon the other valve two 

 corresponding impressions. 



P. sella, Lam. Shell subtetragonal, blackish brown, clouded with 

 greenish white ; valves longitudinally striated and wrinkled. 4 

 to 7 inches long. Inhabits Indian seas Chem. viii. pi. 79, fig. 714. 



P. placenta, Lam. Shell suborbicular, flat, pellucid, white, with 

 longitudinal subdecussated striae. 4 or 5 inches in diameter. In- 

 habits coasts of Tranquebar and China. Lister, pi. 225, fig. 60. 



** Ligament semi-interior ; shell Jbliaceous, often very thick. 



Gen. 12. VULSELLA, Lam. 

 Shell longitudinal, subequivalve, irregular, with beaks equal ; 



hinge with a projecting callosity, depressed above, and a 



conical oblique hollow for the ligament. . 



V. lingulata, Lam. (My a vulsella, Lin.) Shell elongated, depres- 

 sed, transversely striated ; colour pale yellowish brown, with 

 darker longitudinal stripes. 2 to 5 inches long. Inhabits Indian 

 seas. Rumph. Mus. pi. 46, fig. A. 



V. hians, Lam. Shell oblong, subarcuate, tumid, with pale longi- 

 tudinal lines ; posterior sides gaping. Inhabits Indian Ocean 



Lister, pi, 1055, fig. 10. 



