explanation of plates. 445 



Plate 128. 



MQCRB. PAOB. 



84, 85. Area (Noetia) ponderosa, Say. S. Cavolina, . . 255 

 86-88. Tridacna squamosa, Lam. Moluccas, . . . 208 

 89, 90. Tridacna (Hippopus) maculatus. Lam. E. Indies, 209 



91. Tridacna crocea, Lam. Philippines, a, the single ad- 



ductor muscle ; p, pedal muscle, and pedal opening in 

 mantle ; /,the small grooved foot ; &, byssus ; t, labial 

 tentacles; gr, gills; Z, the broad pallial muscle; between 

 g and I is the renal organ ; wi, the double mantle- 

 margin ; s, the siphonal border ; i, inhalent orifice ; e, 

 valvular excurrent orifice (An. Nat. Hist., 1855, p. 

 190), .208 



92. Mj'tilus (Aulocomya) decussatus. Lam. Patagonia, . 262 



93. Mytilus (Caloromya) afer, Grmelin. Algiers, . . 262 



94. Modiola barbata, Linn. Europe, .... 263 



95. Modiola tulipa, Linn. ^. Northern Europe, . . 263 



96. Modiola (Brachydontes) plicatula, Lam. U. S., , 263 



97. Lithodomus caudigeriis. Lam. W. Indies, . . . 263 



98. Lithodomus lithophaga, Linn. ^. Europe, . . 263 



99. Modiolaria impacta, Herm. N. Zealand, . . . 264 

 100. Dreissensia polymorpha, Pallas. Europe, . . . 266 



1-3. Prasina Borbonica, Desh. Isle of Bourbon, . . 26t 



4. Mytilus smaragdinus, Chemn. India, .... 261 



Plate 129. 



5. Area (Granoarca) propatula, Conr. Mio. ; Yirginia, . 254 



6. Area (Trigonarca) triquetra, Conr. Cret.; N, Carolina, 25t 



7. Megalomus Canadensis, Hall. Onondaga Salt Group, 



New York, 257 



9. Megambonia aviculoidea. Hall. L. Helderberg Group, 



New York, 258 



10. Pachymytilus petasus, d'Orb. Jurassic ; France, . 267 



11. Mytilus (Mytiloconcha) incurva, Conr. Miocene; U. 



States, 262 



12. Modiola (Advda) soleniformis, d'Orb. Peru, . . 263 

 IB, 14. Orthonota contracta, Conr. L. Sil. ; U. S., . . 154 



15. Modiomorpha concentrica, Conr. Hamilton Group, 



New York, 2 9 



16. Lithodomus (Botula) splendida. Hunker. Australia, . 263 



17. Crenella decussata, Mont. Boreal Seas, . . . 264 



18. Crenella (Nuculocardia) divaricata, d'Orb., . . . 264 



19. Crenella (Dacrydium) vitreum,Moller. Norway, . 264 



20. Arcoperna filosa, Conr. Eocene; Mississippi, . . 264 



21. Myrinapelagica, Forbes. Cape of Good Hope, . . 265 



22. Dreissensia (Praxis) Sallei, Recluz. W. Indies, . . 266 



23. Septifer Heberti, Desh., . . 266 



