384 AXEL A. OLSSON 



American species to the Eocene shell is merely superficial. Two fossil forms 

 of Lyratellina are now known, L. protolyra (Anderson) from Miocene of 

 Colombia, and L. aequizonata (Pilsbry and Olsson) from the Pliocene of 

 Ecuador. 



There are two species in the Panamic-Pacific region. 



I. Beaks high and sharp, the valve margin in front deeply excavated. Con- 

 centric lamellae of the surface sculpture of medium size, spaced about a 

 millimeter apart. 



L. lyra 



II. The beaks are lower, the margin in front not deeply excavated. Con- 

 centric lamellae much finer and spaced three to a millimeter. 



L. lyrica 



Lyratellina lyra (Hanley) Plate 70, figures 1-lc 



Tellina lyra Hanley, 18+4, Proc. Zool. Soc. London, p. 68 Tumbez.— Hanley, 1846, Thes. 



Conch., vol. 1, Tellina, p. 271, pi. 62, fig. 187. — Sowerby, Conch. Icon., vol. 



17, Tellina, pi. 36, fig. 203. 

 Tellina (Macaliopsis) lyra Hanley, Maxwell Smith, 1944, Panamic Marine Shells, p. 



64, fig. 842. — Hertlein and Strong, 1949, Zoologica, vol. 34, pt. 2, No. 9, p. 81. 



Shell elliptical, compressed, thin, the anterior side higher, more rounded, 

 the posterior side with its dorsal margin descending. Rostral area as long as 

 the posterior side, narrow, excavated and well sculptured. Sculpture consists 

 of small, regular, thin, sharp concentrics separated by flattened interspaces 

 about a millimeter wide. The pallial sinus is large, its highest point forming 

 an acute angle a short ways in front of and on level with the middle of the 

 posterior adductor scar, its end rounded, its lower limb confluent with the 

 pallial line. 



A rare species. The largest specimen seen, a right valve from the beach 

 at Fort Amador, Balboa, measures: length 56.2 mm., height 39.6 mm., diam- 

 eter 6 mm. 



Range — Lower California to northern Peru. Off San Salvador and 

 Guatemala (H. and S.). Panama: Bucaro. Panama Canal Zone: Fort 

 Amador beach. Ecuador: Sua; Mompiche. Peru: Tumbez (type locality). 



Lyratellina lyrica (Pilsbry and Lowe) Plate 70, figures 6, 6a 



Tellina (Macaliopsis) lyrica Pilsbry and Lowe, 1932, Proc. Acad. Nat. Sci., Philadelphia, 

 vol. 84, p. 94, pi. 10, figs. 4, 4a. — Hertlein and Strong, 1949, Zoologica, vol. 34, 

 pt. 2, No. 9, pp. 81, 82. 



The shell is generally smaller, more elliptical than L. lyra with much 

 finer sculpture formed by evenly spaced, concentric threads spaced about 

 three to a millimeter. The escutcheon is deep and narrow. According to 

 Hertlein and Strong, the exterior of perfectly fresh specimens show a brilliant 

 iridescence of spectral colors caused by the fine growth lines between the 

 larger concentrics acting as a diffraction grating. The species occurs fossil 

 in the Pliocene of Ecuador. A perfect specimen (bored) obtained by shrimp 

 trawlers off Punta Malo, Panama, measures: 



Length 45.8 mm., height 32.8 mm., diameter 14.3 mm (closed valves; 

 from Mr. and Mrs. H. B. Johnson, Rodman, Canal Zone). 



Range — Lower California to Panama and probably Ecuador. 

 Panama: Off Punta Malo; Gulf of Chiriqui (Hertlein and Strong). Mexico: 



