WHITE ON NEW INVEETEBRATES. 715 



Genus KEEITINA Lamarck. 



Neritina naticiformis (sp. nov.). 



Shell small, sabglobose in aspect, being more nearly like that of Natica 

 than the usual forms of J^eritina, due mainly to the greater elevation of 

 the apex, consisting of three or four volutions, which so rapidly increase 

 in size that the last one comprises much the greater i)art of the bulk of 

 the shell; all the volutions regularly convex, the suture being distinct; 

 test not massive; aperture large, nearly straight on the inner side, and 

 regularly convex on all other sides, the whole comprising more than a 

 semicircle; edge of the outer lip thin ; inner lip moderately broad, flat- 

 tened, apparently smooth, sloping strongly inward, or away from the 

 outer lip ; inner margin of the inner lip somewhat concave, apparently 

 without crenulations. 



Surface marked by numerous distinct lines of growth, and upon some 

 examples traces of revolving strice have been detected, especially upon 

 the proximal or lower portion. 



Extreme length from apex to front margin 6 millimeters; greatest 

 diameter of the last volution, across the middle of the aperture, about 

 the same. 



In general aspect, this little shell so closely resembles a Natica that, 

 the apertures all being filled with the imbedding material, the first 

 suggestion that it might not belong to that or a closely allied genus came 

 from its association with fresh- and brackish-water forms. Upon break- 

 ing up some of the examples, the inner lip was found to be more charac- 

 teristic of Neritina than Natica, although it is not so broad and char- 

 acteristically developed as is usual in the former genus. In this respect^ 

 and in the moderately thin test, it departs from typical forms of Neritina. 



Position and locality. — Laramie Group, Bear River Valley, near the 

 mouth of Sulphur Creek, Wyoming. 



Subgenus Velatella Meek. 



Neritina ( Velatella) haptista (sp. nov.). 



Shell small, elliptical in outline, broadly convex above, the convexity 

 of the postero-median portion being greater than elsewhere, nearly flat 

 beneath ; umbo prominent, nucleus or apex posterior, minutely subspiral 

 and only a little elevated above the posterior margin, small, closely 

 incurved, and turned to the right side; inner lip broad, smooth, slightly 

 convex in all directions, and occupying fully one-half of the under sur- 

 face of the shell ; outer lip apparently moderately thin, but this feature 

 has not been clearly seen. 



Surface so nearly smooth as to give the shell an almost polished 

 appearance, but under the lens minute striae of growth are visible, 

 and also especially near the borders minute radiating strise are seen, 

 apparently in the substance of the shell. In addition to this, there are, 

 upon the only example discovered, seven or eight irregular radiating 



