426 bulletin: museum of comparative zoology. 



ANOMALODESMACEA. 

 Anatinacea. 



(A. EUSIPHONIA.) 



Periplomatidae. 

 PERIPLpOMA Schumacher. 



Periploma carpenter! Dall. 



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. stearnsii Dall, and is best described 

 bv comparisou with it. In P. steanisii the shell is somewhat less inflated and the 

 beaks are nearer the posterior end, but nearer the anterior end in P. carpenteri ; in 

 the latter the surface granules are more crowded and coarser, and not arranged in 

 rows separated by a clear space, as in P. stearnsii ; the rostrum in P. carpenteri 

 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, with a height of 39 and a length of 47 mm. 



Only one right valve was dredged, in the Gulf of Pauama, at the U. S. 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 Dall. 



Plate 16, figure 6. 



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 Cue 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 slighily excavated ; interior faintly 

 pearly; pallial sinus large, rounded, shallow ; chondrophore strong, spoon-shaped, 

 inclined obliquely forward. Lengtli of shell, 40; lioight, 35.5 ; diameter of the 

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

 total diam. 13 mm. 



