310 WEST SOUTH AMERICAN SHELLS STEARNS. 



19. Area (Scapharca) labiata Sby. 



.Four valves. 

 Babia. 



20. Area (Byssoarca) Reeviana Orb. 



A single perfect valve of a youug example. 

 Manta. 



21. Pectunculus (Axinaea) iuaequalis Sby. 



Two valv^es. 



Panama; Payta; oue from each place. 



22. Crassatella gibbosa Sby. 



Four odd valves of this exceedingly rare species, measuring from 2^ 

 to 1t6 inches in breadth. 



Payta ; it ranges northerly to the Gulf of California. 



23. Diplodonta obliqua Rve. 



Three odd valves. 

 Panama. 



24. Cardita laticostata Sby. 



One perfect specimen, also odd valves. 

 Panama. 



25. Chaiua echiuata Brod. 



Several odd valves from each of the following places : 

 Manta: Payta. * 



26. Cardium senticosum Sby. 



Several odd valves. 



Manta; Payta. 



The examples from Payta show thirty-six ribs. C. muricatiim, the 

 Antillean analogue o{ senticosum^ has thirty-three. The Mediterranean 

 C. erinaceus, a species of quite distinct aspect, also has thirty-six. G. 

 rastrum Rve. (Conch Icon. Mon. Cardium, PI. xvi, fig. 82), is the same as 

 senticosum as implied by Reeve's substitution of the latter name for 

 rastrum in the index to his monograph. 



The number of ribs in senticosum as in other related species of the 

 general group that I hav^e examined varies somewhat. Carpenter's 

 Mazatlan examples of senticosum show as many as forty. 



27. Cardium procerum Sby. 



Numerous odd valves. 

 Bahia; Manta; Payta. 



The characteristic and striking obliqueness of this species so conspicu- 

 ous in the adults is hardly noticeable in the young shells. The number 



