FAMILIES AND GENERA. IOI 



Lyonsiidse. (EDLAMELLIBRANCHIATA.) Plate xv. 

 Lyonsia, 173. 



MaetridSB. (EULAMELLIBRANCHIATA.) Plate ix. 



Amphidesma, teeth of unequal size in both valves, 107. 

 Mactra, teeth of unequal size in right valve only, 108-112. 



MarglnellidSB. (PROSOBRANCHIATA.) Plate xxix. 

 Marginella, 529. 



Murieidae (PROSOBRANCHIATA.) Plate xxvi. 



Trophon, canal open throughout, outer lip not notched within, 



503-505- 

 Lachesis, canal open throughout, outer lip notched within, canal 



short and wide, 510. 



Murex, canal covered over, 506, 507. 



Ptoi'pura, pillar flattened, sloping inwards with a sharp edge, 

 508, 509. 



MyidSB. (EULAMELLIBRANCHIATA.) Plate xii. 



My a, upright spoon-shaped cavity for cartilage, under beak of 

 right valve, 143-145. 



Corbula, right valve overlapping left, 146. 



Lutraria, hinge plate projecting in the middle, 147,^48. 



Mytilidae. (FILIBRANCHIATA.) Plate ii. 



Crenella, shell striated all over; hinge with an upright tooth, 

 24, 25. 



Modiolaria, shell striated only at ends, 26-29. 



Mytilus, shell oblong triangular, ending in a point and having its 

 two extremities equal, pedal muscular impressions, two in each 

 valve, small, simple, close to the adductors, 19-23. 



NassidcB. (PROSOBRANCHIATA.) Plate xxvi. 

 Nassa, 513-516. 



Naticidse. (PROSOBRANCHIATA.) Plate xxiii. 



Natica, 370-376. 



NePitidse. (PROSOBRANCHIATA.) Plate xxii. 

 Neritina, 356. 



Nueulidse. (PROTOBRANCHIATA.) Plate i. 



Nucula, shell trigonal, lunule cordate, pallial line entire, 1-4. 

 Leda, shell with posterior side produced, lunule lanceolate, pallial 

 line sinuated, 5-8. 



