PANAMIC-PACIFIC PELECYPODA 269 



Tivela (Tivela) lineata (Sowerby) 



Cytherea lineata Sowerby, 1851, Thes. Conch., vol. 2, Cytherea, p. 616, No. 15, pi. 128, 



fig. 26. Hab. unknown. 

 Tivela lineata (Sowerby), Romer, 1865, Monogr. Molluskengating Venus, lAuni bd. 1, 



Tivela, p. 16, No. 24. 

 Tivela subglobosa (Menke), Romer, 1865, op. cit., p. 14, No. 21, pi. 7, fig. 5. 



Shell ovate-trigonal, solid, subequilateral, the length of the shell a little 

 more than their height, the umbones convex and prominent, nearly median. 

 Surface smooth and pohshed, often pure white or marked with transverse, 

 sharply waved, brown lines, sometimes interrupted with irregular radial rays 

 of brown. The dorsal areas are impressed, plain or with feather-like mark- 

 ings of dark brown. Interior white or purple. Hinge heavy. 



Length 31 mm., height 28 mm., diameter 10.6 mm. (right valve, an 

 average specimen). 



Tivela lineata was described by Sowerby from an unknown locality. 

 Pure white shells from Panama with feather-like markings on the dorsal 

 slopes agree quite well with Sowerby's figure of T. lineata in the Thesaurus. 

 Completely white shells also resemble Romer's figure of T. arguta (Menke). 

 T. lineata appears to be distinct from T. byronensis, differing by its larger 

 and wider umbones. 



Range — Panama. Panama: Pearl Islands; Las Tablas; Punta Pajaron 

 (USNM 603409). 



Subgenus PIAIflTITELA, new subgenus 



Tlyela (PlanltlTela) planulata (Broderip and Sowerby) Plate 44, figures 5, 5a 



Cytherea planulata Broderip and Sowerby, 1829, Zool. Jour., vol. 5, p. 48.— Sowerby, 



1839, Zool. Beechey's Voyage, p. 151, pi. 43, fig. 6.— Sowerby, 1851, Thes. 



Conch., vol. 2, p. 618, No. 20, pi. 127, fig. 13.— Reeve, 1864, Conch. Icon., vol. 



14, Cytherea, pi. 8, figs. 34 a, b. 

 Cytherea planulata, var. suffusa Sowerby, 1835, Proc. Zool. Soc. London, p. 46 Salango. 

 Cytherea undulata Sowerby, 1851, Thes. Conch., vol. 2, p. 618, pi. 127, fig. 12.— Reeve, 



1864, Conch. Icon., vol. 14, Cytherea, pi. 8, figs. 33 a, b. 

 Tivela planulata (Broderip and Sowerby), Romer, 1864, Monogr. Molluskengatung 



Venus, Linne, bd. 1, Cytherea, 1. Sectio: Tivela, pp. 8, 9, pi. 3, figs. 2, 2a, 2b. 



Shell of medium or large size (length 60 mm.), subsolid, subtrigonal 

 with fairly convex, submedian umbones, the anterior side a trifle longer. 

 There is no evident posterior gap. Color usually a straw-yellow with large 

 radial rays of brown. Lunule large, usually ill-defined but with its surface 

 covering most of the flattened dorsal submargin. Pallial sinus short but 

 distinct. 



Length 61.4 mm., height 47.5 mm., diameter 27.2 mm. Boca Pan, 

 Length 58 mm., height 46.9 mm., diameter 24.8 mm. Manglaralto. 



This species replaces T. hians north of Cabo Blanco in Peru and from 

 which it is distinguished by its more solid, convex valves, stronger color and 

 in the absence of a posterior gap. It may show considerable variation in 

 shape and in surface markings which have resulted in some duplication of 

 names. Small or medium-sized specimens from Panama with a rich color 

 resemble the shell figured by Sowerby as T. suffusa based on a specimen 



