426 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
ANOMALODESMACBEA. 
Anatinacea. 
(A. EustpHonta.) 
Periplomatidae. 
PERIPLOMA ScHuMACHER. 
Periploma carpenteri Datt. 
Plate 16, figure 8. 
Periploma carpenteri Dall, Proc. U. S. Nat. Mus., 1896, 18, p. 20. 
This species is of much the outline of P. stearnsti Dall, and is best described 
by comparison with it. In P. s¢earnsii the shell is somewhat less inflated and the 
beaks are nearer the posterior end, but nearer the anterior end in P. carpenteri ; m 
the latter the surface granules are more crowded and coarser, and not arranged in 
rows separated by a clear space, as in P. stearnsit ; the rostrum in P. carpentert 
is less distinctly marked off from the arch of the base, the epidermis has a more 
greenish tint, the interior is more pearly, with a larger pallial sinus, and the 
chondrophore is wider and vertically, not obliquely, directed. The right valve is 
10 mm. in diameter, witha height of 39 and a length of 47 mm. 
Only one right valve was dredged, in the Gulf of Panama, at the U.8.S. 
“ Albatross’ station 3389, in 210 fathoms, mud, bottom temperature 48°.8 F. 
U.S. N. Mus. 106,891. 
This is the third orbicular species from West America. 
Periploma stearnsii Datu. 
Plate 16, figure 5. 
Periploma stearnsii Dall, Proc. U. S. Nat. Mus., 1896, 18, p. 19. 
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, fissured; left valve slightly less con- 
vex than the right ; rostrum about two thirds as wide as the shell, not strongly 
differentiated, but with the epidermis coarser, and, especially on the left valve, 
more raised and wrinkled, and the basal margin slightly excavated ; interior famtly 
pearly; pallial sinus large, rounded, shallow; chondrophore strong, spoon-shaped, 
inclined obliquely forward. Length of shell, 46; height, 35.5; diameter of the 
right valve, 9 mm.; the rostrum, 20 mm. wide, rounded, and moderately gaping ; 
total diam. 18 mm. 
