198 AXEL A. OLSSON 



angulation and overlain in fresh specimens by a heavy, greenish-brown 

 periostracum which scales off easily from dead shells. Surface color of shell 

 below the periostracum is white, irregular blotched or flushed with purple 

 and pink, and often with scattered narrow or broad bands of deep purple 

 radiating from the beaks. Interior white, deep purple or lighter shades of 

 pink. The pallial sinus is small but distinct. 



Length 41 mm., height 34.7 mm., diameter 21.2 mm. Cojimenes, 

 Ecuador. 



Length 52.1 mm., height 46 mm., diameter 31.6 mm. Ecuador. Para- 

 type (Prime Coll.), MCZ 187454. 



An ovate-subcircular, rather solid shell with a smooth periostracum 

 and rather coarse, regular concentrics. The surface beneath the periostracum 

 is dingy white, faintly tinted with violet or pink and often marked with rays 

 of deeper purple. The posterior-umbonal slope is slightly angled. 



Range — Ecuador to Peru. Ecuador: Cojimenes. Peru: Paita (MCZ 

 176877). 



N^eocyrena meridionalis (Prime) Plate 28, figures 4, 4a, 4b 



Cyrena meridionalis Prime, 1865, Stnitii. Misc. Coll., No. 145, p. 19, No. 12, fig. 14 

 Soutii America, at Payta, in Peru (Cabinet of Prime). 



A small, rounded, globose shell with a dark olivaceous green periostra- 

 cum, the surface below white with purple rays. Interior white flushed with 

 purple over the adductor scars and over the hinge. 



Length 34.7 mm., height 34.5 mm., diameter 26 mm. 



Tumbez, Peru. Lea Coll. USNM 122451. 



Range — Peru. Peru: Tumbez. 



Xeocyrena tribunalis (Prime) Plate 28, figure 1 



Cyrena tribunalis Prime, 1869, Araer. Jour. Conch., vol. 5 (Appendix), p. 148, No. 

 78 (nomen nudum). — Prime, 1870, Ann. Lyceum Nat. Hist. New York, vol. 

 10, p. 300. 



A coarse, heavy shelled species with a sharply folded posterior keel, 

 coarse concentrics and a smooth, dark-green periostracum. 



The holotype seen in Washington, D.C. (MCZ 17688, Prime Coll.), 

 Tucames River has the following measurements: length 55 mm., height 

 45.8 mm., diameter 34.5 mm. 



The location of Tucumes River could not be determined; it is probably 

 in Ecuador or Colombia. 



Neoeyreaa radiata (Hanley) Plate 2%, figures 5-5c; 



Plate 85, figures 2-2c 



Cyrena radiata Hanley, 1844, Proc. Zool. Soc London, p. 159 Realejo, Nicaragua.— 

 Prime, 1865, Smith Misc. Coll. No. 145, p. 13, No. 14, fig. 7.— Sowerby, 1876, 

 Conch. Icon., vol. 20, Cyrena, pi. 11, figs. 47a, b. 



Shell of medium size, ovately rounded, with full, prominent umbones, 

 slightly off the middle line, the small beaks directed anteriorly. Valves are 

 strongly convex, solid. There is an indistinct posterior-umbonal angle which 

 sets off a wide but poorly differentiated dorsal area. There is no lunule. 

 Periostracum dark olivacesous, generally intact over the whole surface, 

 often showing one or more radial rays faintly at the ventral margin. Be- 

 neath the periostracum, the surface is marked with somewhat irregular, 



