1901.] NATURAL SCIENCES OF PHILADELPHIA. 397 



NERITID^. 

 Nerita martensiana n. sp. 



Shell globose, small, solid, rather bright sulphur yellow, paler 

 and somewhat mottled with gray or blackish toward the aperture. 

 Surface dull, sculptured with low, rather coarse spii'al cords, about 

 15 on the last whorl, the upper one appressed against the preceding 

 whorl. Spire short, whorls about 3, the last a little depressed below 

 the suture, which is bordered below by a somewhat more promi- 

 nent cord. Aperture semicircular, yellow or Avhitish; lip-rib 

 smooth, with a small tubercle above, and another well within near 

 the base of the columella. Columellar area white or yellowish, flat 

 and smooth, the outer border well defined; edge of columella 

 straight, with two or three low, subobsolete teeth, the upper one 

 strongest. 



Alt. 10, diam. 9.5 mm. 



Loo Choo Islands (Mr. Y. Hirase). Types No. 80,489 Coll. 

 A. N. S. P., from No. 729 of Mr. Hirase's collection. 



Small as this species is, the specimens are apparently adult. The 

 smooth columellar area, wnth well-defined outer margin, weak 

 deuticulatiou and smooth rib within the outer lip are its more 

 prominent characters. I find no species agreeing with these sj^eci- 

 mens in the monographs, the best of which is that by Prof, von 

 Martens in the new edition of Chemnitz. 

 Nerita helicinoides var. tristis nov. 



Shell black with some white spots along the basal margin, and 

 sometimes a few angular pink and white spots elsewhere. Colu- 

 mella three-notched in the middle; area smooth, yellow-tinted in 

 the middle; lip-rib weakly crenulate, a small denticle near its 

 upper end. 



Alt. 13|, diam. 11^ mm. 



Loo Choo Islands (Mr. Y. Hirase, No. 218). Types No. 80,406 

 CoU. A. N. S. P. 



This variety is like tne typical form in the deuticulatiou of 

 columella and lip. In var. Icevilabris Pils. the lip-rib is smooth 

 throughout, and the columellar denticles very weak; these charac- 

 ters being constant in a large number of specimens. 



N. helicinoides is apparently closely related to the small form of 

 y. striata Burrow described by Prof, von Martens in the new edi- 

 tion of Chemnitz, p. 39, PI. 7, figs. 19, 20. 



