408 AXEL A. OLSSON 



Shell of medium size (to about 47 mm.), obliquely subovate to sub- 

 trigonal, the anterior side longer, higher, its dorsal margin somewhat ex- 

 panded, the posterior side shorter, pointed, pinched but with hardly any 

 flexing. The valves are nearly equal, moderately convex, especially along 

 the anterior umbonal slope, slightly depressed on the posterior-ventral 

 slope. Valves are relatively thin, smooth except for fine, growth concentrics, 

 the color for the most part white, but some shells have the umbones and 

 the shell cavity within flushed with pink; periostracum is thin, light-cream 

 color. 



Length 40.8 mm., height 38.2 mm., diameter 15.5 mm. 



Young shells may resemble T. Uneata Turton of the Caribbean but are 

 more elliptical, thinner, and more convex. Most specimes are white, but 

 occasional specimens have the umbones stained with rose or pink. This 

 appears to be a localized species; it is common at Old Panama. 



Range — Panama. Panama: Old Panama. 



Genus SCROBICULINA Dall, 1900 

 Type species by original designation, Scrobicularia viridotincta Car- 

 penter. Gulf of California. 



(Schumacheria Cossmann, 1902, was proposed to replace Scrobiculina 

 Dall, 1900, because of Scrobiculinus Monterosato, 1884, but now thought 

 unnecessary.) 



The shell is large or medium-sized, relatively thin, subovate, the um- 

 bones and beaks near the middle line, the posterior side narrower and 

 flexed at the end. The hinge has two cardinal teeth in each valve but the 

 posterior one often becomes partly effaced or wholly elirninated by the 

 encroachment of the ligament scar in large specimens; the right or anterior 

 lateral tooth is placed close to the cardinals. Ligament external but becomes 

 deeply immersed into the hinge plate, its scar short and high. Surface ap- 

 proaching smoothness except for fine concentric threads, the left valve 

 somewhat more plain but often showing faint radial lines. The pallial 

 sinus is of moderate size, discrepant in the two valves, lower and narrower 

 in the left. 



This genus resembles Macoma in the shape of its valves and by its 

 deeply immersed ligament, but the hinge is provided with an anterior 

 lateral tooth. 



Scrobicnllna viridotincta (Carpenter) 



} Scrobicularia -virido-tincta Carpenter, 1856, Proc. Zool. Soc. London, p. 160 Panama. 



Macoma viriditincta (Carpenter), Stearns, 1894, Proc. U. S. Nat. Museum, vol. 17, p. 

 156 La Paz and several other localities in the Gulf of California. 



Tellina {Scrobiculina) viridotincta (Carpenter), Dall, 1900, Proc. U. S. Nat. Museum, 

 vol. 23, p. 302.— Hertlein and Strong, 1949, Zoologica, vol. 34, pt. 2, pp. 66, 67. 

 — Hertlein and Strong, 1950, op. cit., vol. 35, pt. 4, pi. 1, fig. 14.— Myra Keen, 

 1958, Seashells of Tropical West America, p. 176, fig. 415. 



Tellina viridotincta (Carpenter), Pilsbry and Lowe, 1932, Proc. Acad. Nat. Sci. Phil- 

 adelphia, vol. 84, p. 133. 



The shell is relatively large, subovate in shape, depressed to slightly 

 convex, the posterior side short and narrow, slightly flexed towards the 

 right at the end. Color white but usually more or less deeply flushed with 

 yellow or orange. 



