1908.] NATURAL SCIENCES OF PHILADELPHIA, 557 



which projects as a free lobe, the middle or lower part projecting 

 beyond the adnate upper border; hence the general outhne of the callus 

 is semicircular. The lower lobe of the callus is ordinarily larger than 

 the upper. The inner part of the umbilical excavation is covered 

 with yellowish cuticle except in old or worn shells, as it is in all the 

 related forms; and while there may be two or three narrow radial 

 purplish streaks, the umbilicus is mainly white within. The exterior 

 is more or less deeply tinted with chestnut or livid brown above, 

 paler or white on the base; the early whorls are dull blue with a pale 

 subsutural band, apex dark red. The inside of the aperture is chestnut 

 above, white at the base. 



Most of the specimens before us are from China. One lot is labelled 

 Madras. The type locality was not known. Absolute synonyms of 

 this form are Natica lamarckii Recluz, and N. lamarckiana "Recluz," 

 Rve. 



Polinices didyma bicolor (Phil.). PI. XXIX, figs. 4, 5. 



A form of didyma which may perhaps be segregated, as a subspecies 

 was described as N. hicolor Philippi. It is smaller than P. didyma 

 ampla, the maximum diameter 35 to 39 mm. Umbilicus and umbilical 

 callus similar, but the lobes of the latter are often more convex, and 

 darker, very dark chestnut or chocolate colored. Upper surface 

 darker than in didyma or didyma ampla, generally bluish or somewhat 

 plum colored, with darker and paler streaks; base and interior of 

 umbilicus pale or pure white. Interior of the aperture very dark 

 chestnut or chocolate with a white area at the base. 



This form differs from didyma and didyma ampla chiefly by the 

 more strongly contrasted colors and smaller size. While not strongly 

 differentiated, it seems to be recognizable, and not uncommon. 



Type locality China Sea. Specimens are before us from "China," 

 Singapore and Queensland. 



Natica peiiveriana Recluz is identical with hicolor. 

 Polinices didyma vesicalis (Phil.). PI. XXIX, figs. 6. 7. 



Similar to P. didyma, but the base and interior of the umbilicus are 

 generally conspicuously streaked radially ivith hroum; upper surface 

 light brownish, as in didyma; there is a more or less definite white 

 band or paler area between the basal and the upper tinted tracts. 

 This band is usually more distinct inside. Upper adnate edge of the 

 callous lobe generally longer than in P. didyma ampla Phil., more as 

 in didyma, but the callus is smaller. The whole parietal wall and 

 adjacent root of the callous lobe are covered with a heavy pure white 

 callus, whereas in didyma ampla Phil, this white area is much less 

 36 



