PANAMIC-PACIFIC PELECYPODA 65 



smoothish space along the rostral carina. On the anterior, rounded slope, 

 the concentric riblets are flexed slightly by an impressed ray. Interior of 

 the shell shows its solid build, the adductor scars being deeply impressed, 

 the pallial line also impressed and showing a small, shallow sinus. Hinge 

 plate is relatively large and stout, the hinge teeth strong and with approxi- 

 mately the same number in each set. 



Length 15.5 mm., height 10.5 mm., diameter 7 mm. 



This is a deepwater species from the Gulf of Panama. The posterior- 

 dorsal side is nearly straight, the two ends of the shell appearing subequal. 

 Sculpture is fine and close. A similar species (N. chiriquiana Olsson) occurs 

 in the Pliocene of the Burica Peninsula. 



Range — Panama. 



Ifuculana (Saccella) acapnlcensis (Pilsbry and Lowe) Plate 2. figures 8, 8a 



Leda (Saccella) acapnlcensis Pilsbry and Lowe, 1932, Proc. Acad. Nat. Sci. Philadelphia, 

 vol. 84, p. 107, pi. 17, figs. 1, 2 Acapulco, Mexico in 20 fathonas. 



Nuculana (Saccella) elenensis (Sowerby), Hertlein and Strong, 1940, Zoologica, vol. 25, 

 pt. 4, No. 25, pp. 393, 394, pi. 1, figs. 12, 14, IS, 16, 22. (Not A^. elenensis 

 Sowerby, 1833.) 



The shell is rather solid, plump, white under a thin light grayish-olive 

 periostracum. Anterior end rounded but with somewhat uneven outline, 

 posterior end produced, rostrate, tapering to a narrow point, the dorsal 

 slope concave behind, the edges of the valves projecting very little above 

 the posterior keel. Ventral margin strongly arcuate, straight or even slightly 

 concave close to the posterior point. Lunule not sunken, very narrowly 

 lanceolate, transversely costulate; posterior dorsal area broadly lanceolate, 

 bounded by a rounded rib in each valve, a little convex in the middle, con- 

 cave along the ridges, longitudinally costate in continuation of the ex- 

 ternal concentric ridges, which are a little enlarged as they pass over the 

 posterior rounded rib or keel. Sculpture of regular concentric costae about 

 as wide as their intervals. Towards the ventral margin the ridges have 

 abrupt lower margins. The interior is white. Hinge with about 14 well-de- 

 veloped teeth on each side of the broadly triangular resilium, and with a 

 group of about six minute, narrow teeth behind, and about 10 before the 

 resilium. Pallial sinus small, rounded at the end. 



Length, 13.2 mm., height 7.0 mm., diam. 5.0 mm. 



Length, 15.3 mm., height 8.3 mm., diam. 6.3 mm. — (Pilsbry and Lowe.) 



This form was united with N. elenensis by Hertlein and Strong (fol- 

 lowed also by Myra Keen) but it appears to be a distinct species, differing 

 from N. elenensis by its longer form, less convex valves, and by its more 

 regular and sharper sculpture. The anterior slope bears sometimes a weakly 

 indented ray. 



Range — Mexico to Ecuador. Mexico: Acapulco. Ecuador: Esmeraldas. 



Ifucniana (Saccella) hindsii (Hanley) 



Leda hindsii Hanley, 1860, Proc. Zool. Soc. London, p. 440 Nicoya. — Hanley, in Sowerby 



1860, Thes. Conch., vol. 3, Nuculidae, p. 135, sp. 51, pi. 229, fig. 102. 

 Nuculana hindsii (Hanley), Hertlein and Strong, 1940, Zoologica, vol. 25, Pt. 4, p. 4D4. 

 Nuculana (Saccella) hindsii (Hanley), Tucker Abbott, 1954, American Seashells, p. 339 



Shell small (length about 8 mm.), light yellowish brown, ovate-oblong, 

 inequilateral, more or less vientricose with a conspicuous indented ray on 

 the anterior slope. The sculpture of closely spaced concentric riblets cover 



