PANAMIC-PACIFIC PELECYPODA 71 



to be the same species, as confirmed by J. R. Le Brocton Tomlin after 

 examination of the type at the British Museum (Natural History). 



Range — Coast of Ecuador and northwestern Peru. Peru: Punta Picos; 

 Zorritos; Tumbez. Ecuador: Ancon Point; Santa Elena; Punta Blanca; 

 Canoa. 



Adrana exoptata (Pilsbry and Lowe) Plate 3, figure 6 



Leda (Adrana) exoptata Pilsbry and Lowe, 1932, Proc. Acad. Nat. Sci. Philadelphia, 



vol. 84, p. 107, pi. 17, figs. 8, 9. 

 Adrana exoptata (Pilsbry and Lowe), Hertlein and Strong, 1940, Zoologica, vol. 25, 



pt. 4, pp. 409, 410, pi. 2, fig. H.— Hertlein and Strong, 1955, Bull. Araer. Mus. 



Nat. Hist., vol. 107, art. 2, pp. 170, 171, pi. 3, figs. 6, 7. 



Shell small (length usually less than 20 mm.), elongate, compressed, 

 the anterior side somewhat higher and shorter. Dorsal margin is not quite 

 straight. Sculpture is formed by fine, threadlike ridges concentrically ar- 

 ranged on the anterior part, straightening out and sloping towards the 

 ventral margin and crossing the lines of growth obliquely on the middle 

 and posterior sides. A smooth radial band lies below and in front of the 

 posterior carina; this smooth zone may be narrow with the sculpture ending 

 sharply against it or the band may be wider if the sculptural ridges fade out 

 towards it in a more irregular manner. 



TTiis is a small species seldom exceeding 17 mm. in length and easily 

 recognized by the sculpture becoming oblique on the middle and posterior 

 sides of the disk. The smooth band below the posterior carina is variable 

 in its development and in some shells may be lacking. 



Range — ^Mexico southward to Ecuador. Mexico: Guaymas; Tangola- 

 Tangola. Panama: Pearl Islands; Pina Bay; (Hertlein and Strong). 

 Colombia: Ardita Bay; Aquacata (Hertlein and Strong). Ecuador: Off 

 Cabo Pasado (Hertlein and Strong); Esmeraldas. 



Adrana tonosiana (Pilsbry and Olsson) Plate 3, figures 11, 11a 



Nuculana (Adrana) tonosiana Pilsbry and Olsson, 1935, Nautilus, vol. 48, No. 4, pp. 

 117, 118, pi. 6, fig. 4.— Hertlein and Strong, 1940, Zoologica, vol. 24, pt. 4, 

 No. 25, p. 412, pi. 2, fig. 15. 



This species closely resembles A. crenijera (Sowerby), which it seems 

 to replace to the northward of Ecuador. A. tonosiana is much smaller, 

 proportionately shorter and higher, with coarser sculpture on a band below 

 the anterior-dorsal angle, the concentric threads spreading apart, dividing 

 and with an intercalary threadier appearing between them along the um- 

 bonal-lunular angle. 



Range — Off Mazatlan to Panama. Panama: Biicaro; Gulf of Chiriqui 

 (Hertlein and Strong). For Guatemala, El Salvador, and Nicaragua records 

 see Hertlein and Strong. 



Family JfTJCINELLIDAE 



Shells mostly minute, obliquely oblong, subtrigonal or egg-shaped, the 

 anterior side short, porcellaneous. Ligament internal seated in a small 

 resilifer bordered by a few, relatively large subtaxodont teeth. 



