PANAMIC-PACIFIC PELECYPODA 421 



Shell elongate, razor or scabbard-shape, concave on the dorsal side. 

 The valves are generally thin, equal in size, each end obliquely truncated 

 and slightly open or gaping. Beaks small, inconspicuous, and placed at 

 the extreme anterior end of the dorsal margin. The ligament is external, 

 attached to a long narrow nymph. The hinge of the right valve has a single 

 vertical directed cardinal tooth and a single lamelliform tooth; the left valve 

 has two cardinal teeth and one horizontal tooth. The anterior adductor scar 

 is elongated and lies in the general direction of the major axis of the shell 

 and about one-fourth its length; the posterior, adductor scar is smaller, 

 and it is placed a distance within the margin. Pallial line is nearly as long 

 as the shell itself, with a wide and shallow sinus at its posterior end. Surface 

 white and smooth except for the usual lines of growth, covered by a ver- 

 nicous periostracum, light brown or straw-yellow in color, often with a dark 

 ray along the length of the umbones. 



This group of razor shells is poorly represented in the Panamic-Pacific 

 fauna. 

 Ensis caljfomicns Dall 



Ensis californicus Dall, 1899, Proc. U. S. Nat. Mus., vol. 22, No. 1185, p. 110 off Island 

 of San Pedro Martir, Gulf of California. — Hertlein and Strong, 1950, Zoologica, 

 vol. 35, pt. 4, p. 227. 



Shell small, slender, arcuate, the sides nearly parallel, the valves being 

 slightly attenuated towards the ends, beaks anterior, the anterior truncation 

 bluntly rounded, the posterior similar; color white with livid pink streaks 

 concentrically disposed; epidermis olivaceous brilliantly polished; hinge with 

 small and very delicate cardinals (usually broken off), one in the right and 

 two in the left valve, the dorsal ridge comparatively strong and elevated, 

 shorter than the ligament. Length of shell, 60 mm.; of dorsal tooth or ridge, 

 5.2 mm.; of ligament, 9 mm.; width of shell, 7 mm.; perpendicular to the 

 chord of the arc formed by the dorsal margin of the valves, 2 mm. (Dall, 

 1899.) 



According to Dall, this small species is similar to the east American 

 E. minor, which, however, differs by being wider distally than in front, 

 larger when adult, with proportionately wider and more arcuate valves. 

 .Specimens may reach a length of 85 mm. The Californian species previ- 

 ously identified as californicus is now known as E. myrae S. S. Berry. 



Range — Gulf of California to Ecuador. Ecuador: Camarones near 

 Esmeraldas. 



Ensis tropicalis Hertlein and Strong Plate 63, figure 3 



Ensis tropicalis Hertlein and Strong, 1955, Bull. Amer. Mus. Nat. Hist, vol. 107, art. 

 2, p. 203, pi. 3, figs. 34, 35 South Passage, Pearl Islands, Panama. 



Shell small, slender, very slightly arcuate, sides nearly parallel, slightly 

 attenuated towards the ends, the anterior end slightly upturned, beaks 

 anteriorly situated, anterior and posterior ends bluntly rounded; color 

 olive-gray, polished; a diagonal line from the beaks to the posterior ventral 

 margin separating a uniformly colored elongated triangular area below from 

 the dorsal area above, the larger portion of it ornamented with brownish, 

 convex markings, the area bordering the dorsal margins nearly uniform in 

 color; hinge with dehcate teeth, one in the right, two in the left; dorsal 

 ridge well developed and a little more than half as long as the ligament. 



