Ligament partly 



in- 



( 8 ) 



6. SOLENIMYA. (SOLEMYA. 



Lam.) M. 



Inequilateral, equival- 4 cardinal tooth on 

 ved, obtuse, at the extre- each valve, dilated, com- tenor and partly exte- 

 mities; a shining epider- pressed, very oblique, rior. (1) 

 mis, projecting beyond slightly concave above, 

 the shell; beaks scarcely receiving the ligament, 

 perceptible, a little gaping 

 on one side. Fig. 17. 



7. Amphidesma. Lam. M. 



Inequilatefal, sub-oval Hinge with 1 or 2 Ligament double, the 

 or rounded, sometimes a teeth and a narrow hoi- external short, the in- 

 little gaping at the sides, low for the inner liga- ternal fixed in the hoi- 

 18. ment ; sometimes with lows. (2) 



lateral teeth. 



DIVISION VI. CONCHjE. 



Fig 



A. Megadesma. Potamo- 

 phila Sower by. Galatea. 

 Lam. F. 



Equivalved, sub-trigo- 

 nal, covered with a green- 

 ish epidermis : inner edges 

 prominent. Fig. 21. 



GENERA. 



2 furrowed cardinal Ligament exterior, 



teeth, approaching at short, projecting and 



base on one valve, 3 on swelling considerably, 



the other, the middle Muscular impressions 



projecting and separa- appearing doubled. (3) 

 ted, lateral teeth wide 

 apart. 



Ligament exterior. (4) 



2. Cyclas. Lam. F. 



Equivalved, ventricose, Cardinal teeth very 

 oval, beaks protuberant, small, sometimes scarce- 

 very fragile. Colour ge- ly any, sometimes 2 on . 

 nerally grey or greenish, each valve, one of which 

 Fig. 22. is folded in two; some- 



times only 1 (folded or 

 lobed) on the one valve, 

 and 2 on the other. La- 

 teral teelh transversely 

 elongated, compressed, 

 lameliiform. 



(1) This ligament is pressed between the tooth and edge of each valve, and 

 shows itself without, enveloping the edge. 



(2) This genus forms a link from the Mactraceae to the Dimyarise, with an exte- 

 rior ligament. 



(3) The only species known, comes from Ceylon and the East-Indies. Mr. 

 Sowerby has lately substituted the name bS Potfiinopliila, because that of Galatea 

 had already been applied by Fabricius to a Crab; but, unfortunately, Latreille, 

 bad established a genus of Crustacece, under the name of Potamophila, upwards of 

 five years ago. N . Regno animal, tome 3, p. 48. I have therefore presumed to 

 propose the name of Megadesma f/zuyst great, Sto-pos a ligamentj. The name of 

 Galalea, being that of a Sea Nymph, was, moreover, by no means well chosen for 

 a Fluviatic shell. 



(4) The exotic Cyclas becomes very large, especially that from Asia. Foss. in 

 Cmg Marl at Betz; the species found at Bctz, resembles the exotic Cyclades more 

 than those of Europe. 



