PANAMIC-PACIFIC PELECYPODA 2S3 



II. Without large spines, the posterior-umbonal angle armed only with 

 small, short spines or scaly nodes at the end of some concentrics. The 

 posterior-dorsal area undivided, 



3. Color white. Concentric riblets rather coarse, some divided at the 

 umbonal angle. 



H. brevispinosa 



4. Surface of shell more strongly colored in shades of violet or chestnut 

 red, the lunule and posterior-dorsal slope deeper colored. Concentric 

 riblets fine and numerous. 



H. rosea 



Hysteroconcha lupanaria (Lesson) Plate 47, figures 1-lc 



Cytherea lupanaria Lesson, 1830, Centurie Zool., p. 196, pi. 64 (four figures.) Between 



Colan and Payta, northern Peru. — Lesson, 1830, Voy. Coquille, Zool., vol. 2, pt. 



1, p. 430. 

 Cytherea Dione var. Broderip, 1835, Proc Zool. Soc. London, pp. 45, 46 Salango and 



Tumbez. 

 Cytheraea lupanaria Lesson, Sowerby, 1851, Thes. Conch., vol. 2, p. 632, No. 69, pi. 



132, fig. 11. 

 Dione lupanaria (Lesson), Romer, 1868, Monogr. Molluskengatung Venus, Linne, bd. 1, 



5. Sectio: Dione Gray, pp. 130-132, pi. 34, figs. 2, 2a, 2b. 

 Pitar {Hysteroconcha) lupanaria lupanaria (Lesson), Maxwell Smith, 1944, Panamic 



Marine Shells, p. 60, fig. 784. 

 Pitar {Hysteroconcha) lupanarius (Lesson), Hertlein and Strong, 1948, Zoologica, vol. 



33, pt. 4, No. 13, pp. 173, 174. 

 Dione semilamellosa Gaudichaud, Reeve, 1863, Conch. Icon., Dione, vol. 14, pi. 6, figs. 



20a, 20b, 20c. 

 Dione exspinata Reeve, 1863, idem, pi. 6, fig. 24. — Romer, 1868, idem, pi. 35, fig. 1 



(as lupanaria {exspinata)). 



Shell often large, ovate, triangular, the beaks nearer the anterior end, 

 the posterior side, therefore, longer, its dorsal margin convex. The surface 

 is sculptured with concentric riblets or lamellae, which may be strong and 

 uniform over the whole disk, or they may become partly obsolete or lower 

 across the middle. On the anterior slope, the alternate riblet is the larger 

 and more lamellose. The posterior-umbonal angle bears a row of large, 

 purple spines (often broken off) which appear to stand backwards and a 

 second row of fewer and smaller spines runs through the middle of the 

 posterior-dorsal area. Most specimens are colored a purple-red or a violet- 

 brown, the space between the spines white, the lunule and posterior-dorsal 

 slope colored a deep purple; rarely, the shell may be pure white or with 

 only minor patches of pale purple. 



Length 53 mm., height 42.5 mm., diameter 28 mm. Negritos, Peru. 



Length 69 mm., height 55 mm., semidiameter 17.5 mm. A left valve, 

 Santa Elena, Ecuador. 



This is the common ''Dione" along the coast of Peru and Ecuador 

 and often attains a length of 70 mm. or more. It is a higher and more 

 rounded form than H. viultispinosa. In young shells, the concentric riblets 

 are strong over the whole surface but with growth, they become lower and 

 subobsolete over the middle of the disk. The color is usually a rich, mahog- 

 any-brown grading into violet red or purple on the sides. 



Range — Lower California to northern Peru. Panama: Guanico. Colom- 

 bia: Isla del Gallo. Ecuador: Mompiche; Manta; Manglaralto; Santa 

 Elena. Peru: Tumbez; Zorritos; Boca Pan; Mancora; Lobitos; Negritos; 

 Paita. 



