526 axel a. olsson 



Explanation op Plate 53 



Figure Page 



1-1 a. Protothaca (Protothaca) thaca (Molina) 304 



Fig. 1, enlargement of hinge; Fig. la, length 55 mm. Lima, Peru. 

 Coll. W. Weywrack. P'RI 25766. 



2-2b. Protothaca (Tropithaca) grata (Say) 305 



Fig. 2, length 36 mm.; Fig. 2a, 2b, length 34 mm. Esmeraldas, Ecua- 

 dor. PRI 25767. 



3-3a. Nioche (Nioche) asperrinia asperrima (Sowerby) 307 



Fig. 3, enlargement of hinge; Fig. 3a, exterior of right valve, length 

 50 mm. Bayovar, Sechura, Peru. PRI 25768. 



4-4a. Nioche (Nioche) asperrima hlstrionica (Sowerby) 307 



Dorsal and external aspects. Length 37 mm. Panama City, Panama. 

 FRI 25769. 



5-5a. Nioche (Jfioche) zorritensis, new species 308 



Fig. 5, a plainly colored shell, length 25 mm. paratype.; Fig. 5a, a 

 smaller shell with zigzag markings, length 19.3 mm. Zorritos, Peru. 

 ANSP 218962. 



6. Nioche (Nioche) asperrima histrlonica (Sowerby) 307 



Holotype, of Venus histrionica Sowerby, length 42. 3 mm. British 

 Museum (Nat. History). 



7. Protothaca (Tropithaca) grata (Say) 305 



Holotype of Venus tricolor Sowerby, length 45 mm. British Museum 

 (Nat. History). 



