212 AXEL A. OLSSON 



Shell small, obliquely rounded, solid, sculptured with 10 to 12, strong, 

 radial ribs, the ribs and interspaces cancellated by evenly spaced, raised 

 concentrics which show especially strong in the deeply grooved interspaces 

 as coarse cross threads, enclosing squarish pits between them. The typical 

 form has the radial interspaces simple but in some shells, the interspaces 

 are wider and have two or more fine, interstitial threads. The posterior- 

 dorsal area is well defined, wide, and sculptured with two strongly scabrous 

 riblets. Internally, the ventral margin is strongly fluted by the ribs and in 

 addition finely crenulated. 



Length 5.5 mm.; height 5.4 mm.; diameter 1,7 mm. (left valve). Isla 

 del Gallo, Colombia. 



Range — Gulf of California to northern Peru. Panama: Biicaro. Colom- 

 bia: Isla del Gallo. Ecuador: Punta Blanca; Santa Elena. Peru: Zorritos. 



Subgenus LUCEflSCA Dall, 1901 



Type species by original designation, Lucina nassula Conrad. West 

 Atlantic, Cape Hatteras to Florida and Cuba. 



Shell small, medium or large, subcircular to subovate, depressed to 

 convex. Surface with a sculpture like that of Codakia, cancellated by the 

 intersection of radial and concentric riblets. Dorsal areas impressed or de- 

 fined by a marked change of sculpture. The hinge with well-developed 

 cardinal and lateral teeth. 



Lucinisca may be confused with Codakia but will be distinguished by 

 its well-developed, depressed dorsal areas. The cancel! ate sculpture is 

 generally sharp or harsh to the touch. 



Lucina (Lucinisca) liana Pilsbry Plate 29, figures 9, 9a 



Lucina muricata Chemnitz, Reeve, 1850, Conch. Icon., vol. 6, Lucina, pi. 8, fig. 46 



Tumbez, Peru. Not L. muricata Chemnitz, 1795 =muricata Spengler, 1798, a 



West Atlantic species. 

 ?? Phacoides (Lucinisca) muricata (Spengler), Dall, 1909, Proc. U. S. Nat. Museum, 



vol. 23, No. 1237, p. 812. 

 Phacoides (Lucinisca) liana Pilsbry, 1931, Proc. Acad. Nat. Sci. Philadelphia, vol. 83, 



p. 435, pi. 41, fig. 3. (P. hispaniolana Li, 1930, not of Maury, 1917). 

 Lucina (Lucinisca) liana (Pilsbry), Hertlein and Strong, 1946, Zoologica, vol. 31, pt. 



3, p. 114. — Hertlein and Strong, 1955, Bull. Am. Mus. Nat. Hist., vol. 107, art. 



2, p. 183 



Young shell less than 10 mm. in length, have a rounded depressed 

 shell and a coarse, lattice-like sculpture of which the ribs are simple, sharply 

 noded by intersecting concentric ridges, their dividing interspaces smooth. 

 As the shell grows larger, it increases in solidity and convexity while small 

 radial threads (one to three) appear in the primary interspaces. 



Average specimens would measure about length 27 mm., height 25 mm., 

 and the diameter of a single valve about 7 mm. 



Common and widely distributed. In the identification of this and the 

 following species, I have followed current practice. It is possible, however, 

 that this Lucinisca is the true fenestrata of Hinds which the original figure 

 of that species resembles. Only an examination of the type of L. fenestrata, 



