462 AXEL A. OLSSON 



the margins well rounded, thin, pearl-white, with a thin, brownish epidermis. 

 Beaks submedian, the umbones moderately convex. Surface smoothish, with 

 lines of growth and fine, submicroscopic, threadlike granules arranged in 

 concentric rows. 



Length 1.98 inches (50.3 mm.), height 1.35 inches (34.3 mm.), diameter 

 17.8 mm. (Holotype, MCZ). 



This species was described from a single left valve now at the Museum 

 of Comparative Zoology at Harvard University. It is a relatively large 

 species with a nearly circular outline and submedian umbone and beak. As 

 suggested by Hertlein and Strong, it seems probable that P. carpenteri Dall, 

 based on a right valve dredged in the Gulf of Panama at 210 fathoms, may 

 represent the same species. 



Range — Panama. Panama: Vicinity of Panama City (C. B. Adams). 



Feriploma (Periploma) carpenteri Dall Plate 82, figures 7, 7a 



Periploma carpenteri Dall, 1896, Proc. U. S. Nat. Museum, vol. 18, No. 1034, p. 20 

 Gulf of Panama, 210 fathoms.— Dall, 1908, Bull. Mus. Comp. Zool., vol. 43, No. 

 6, p. 426, pi. 16, fig. 8. — Hertlein and Strong, 1946, Zoologica, vol. 31, pt. 3, 

 pp. 94, 95. 



This species is similar to P. stearnsii but is more inflated, more orbicular, 

 and with the beaks having a more central position; the granules are said 

 to be coarser and not arranged in separate rows. 



The figure shows the interior and exterior of the type. The original 

 was taken in 210 fathoms of water in the Gulf of Panama. The species has 

 also been recorded by Hertlein and Strong from specimens dredged in three 

 fathoms of water at La Union, San Salvador. P. lucina Olsson from the 

 Pliocene of Panama is an allied species. 



Range — Panama and El Salvador. 



Periploma (Periploma) stearnsii Dall Plate 82, figure 6 



Periploma stearnsii Dall, 1896, Proc. U. S. Nat. Museum, vol. 19, No. 1034, p. 19 off 

 Point Fermin, Gulf of California.— Dall, 1908, Bull. Mus. Comp. Zoo!., vol. 43, 

 No. 6, p. 426, pi. 16, fig. 5. — Hertlein and Strong, 1946, Zoologica, vol. 31, pt. 

 3, p. 95. 



Shell suborbicular, thin, whitish, with pale straw-colored epidermis, 

 sculptured with faint concentric irregularities harmonizing with the lines 

 of growth and by very fine pustules arranged in radiating lines, stronger 

 and more adjacent near and upon the rostrum; beaks not prominent, fis- 

 sured; left valve slightly less convex than the right; rostrum about two- 

 thirds as wide as the shell, not strongly differentiated, but with the epider- 

 mis coarser, and, especially on the left valve, more raised and wrinkled, and 

 the basal margin slightly excavated; interior faintly pearly; pallial sinus 

 large, rounded, shallow; chondrophore strong, spoon-shaped, inclined ob- 

 liquely forwards. Length of shell, 46; height 35.5; diameter of the right 

 valve, 9 mm.; the rostrum 20 mm. wide, rounded, and moderately gaping; 

 total diameter, 18 mm. 



This differs from P. discus, Stearns, in the radial arrangement and 

 larger size of its surface granules, its wider rostrum and more compressed 

 form. (Dall, 1896.) 



Figure 6, Plate 82 shows the exterior of the holotype, 110548 U. S. Nat. 



